The Journal of Pathology

Changes in the tumour microenvironment mark the transition from serous borderline tumour to low‐grade serous carcinoma

AbstractLow‐grade serous ovarian carcinoma (LGSC) is a rare and lethal subtype of ovarian cancer. LGSC is pathologically, biologically, and clinically distinct from the more common high‐grade serous ovarian carcinoma (HGSC). LGSC arises from serous borderline ovarian tumours (SBTs). The mechanism of transformation for SBTs to LGSC remains poorly understood. To better understand the biology of LGSC, we performed whole proteome profiling of formalin‐fixed, paraffin‐embedded tissue blocks of LGSC (n = 11), HGSC (n = 19), and SBTs (n = 26). We identified that the whole proteome is able to distinguish between histotypes of the ovarian epithelial tumours. Proteins associated with the tumour microenvironment were differentially expressed between LGSC and SBTs. Fibroblast activation protein (FAP), a protein expressed in cancer‐associated fibroblasts, is the most differentially abundant protein in LGSC compared with SBT. Multiplex immunohistochemistry (IHC) for immune markers (CD20, CD79a, CD3, CD8, and CD68) was performed to determine the presence of B cells, T cells, and macrophages. The LGSC FAP+ stroma was associated with greater abundance of Tregs and M2 macrophages, features not present in SBTs. Our proteomics cohort reveals that there are changes in the tumour microenvironment in LGSC compared with its putative precursor lesion, SBT. These changes suggest that the tumour microenvironment provides a supportive environment for LGSC tumourigenesis and progression. Thus, targeting the tumour microenvironment of LGSC may be a viable therapeutic strategy. © 2024 The Pathological Society of Great Britain and Ireland.

Metamorphoses in pancreatic cancer precursors: the role of simple mucinous cysts †

Abstract Pancreatic cystic lesions present a unique opportunity to identify and potentially prevent pancreatic ductal adenocarcinoma (PDAC), one of the deadliest solid tumors. Until now, research has primarily focused on intraductal papillary mucinous neoplasms (IPMNs) and mucinous cystic neoplasms (MCNs), whose potential for malignant transformation is well established. In recent years, however, a new pathological entity has emerged: the simple mucinous cyst (SMC). SMCs are distinct from other cystic lesions, as they lack both communication with the pancreatic ductal system (a hallmark of IPMNs), and the ovarian‐like stroma, characteristic of MCNs. The recent work by Pea et al , published in The Journal of Pathology , suggests that these lesions can progress to PDAC, underscoring the need for further characterization. In this commentary, we review the key findings of this study and discuss the potential next steps required to translate these discoveries into actionable clinical practice. © 2025 The Pathological Society of Great Britain and Ireland.

Identification of actionable targets using DEPArray ‐based sorting of pure carcinoma and stromal populations from formalin‐fixed paraffin‐embedded tissues followed by shallow whole‐genome sequencing

Abstract Formalin‐fixed paraffin‐embedded (FFPE) tissue specimens represent precious resources for clinical genomic profiling studies, especially when coupled with comprehensive medical records. Even though next‐generation sequencing (NGS) is an effective tool to detect somatic mutations and somatic copy number alterations (sCNA), the biggest challenges in unlocking clinically translatable genomic information from FFPE tissue are low DNA yields and degraded DNA, affected by variable formalin fixation. Another issue is that the proportion of carcinoma and other noncarcinoma cells is variable and can be confounded by intratumoral heterogeneity. To explore these challenges, we isolated pure carcinoma and stromal cells using the DEPArray™ NxT system, a microchip‐based digital sorter that allows isolation of pure, homogeneous subpopulations of cells from FFPE samples. We isolated pure carcinoma and stromal cell populations from 12 FFPE tissues, including tissues from nine primary and metastatic breast cancer and three primary ovarian high‐grade serous carcinomas. This was followed by downstream shallow whole‐genome sequencing (WGS) for copy number landscape profiling (10 samples) and/or a targeted panel for somatic mutation and sCNA analysis (seven samples), subject to cell availability. Seven out of 10 samples (even some with low tumour content or of old age) produced good‐quality genomic data, detecting sCNA in all carcinoma population samples but not in the stromal populations. Mutation analysis was performed successfully in 6/7 samples and somatic mutations were detected in all of them. Our workflow enabled the identification of clinically actionable targets, including PIK3CA, ERBB2, FGFR1/2, CDK6, CCNE1, KRAS amplifications and RB, BRCA1/2 losses in patients that would direct therapy. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Androgen receptor‐mediated regulation of BRCA1 modulates the antioxidant defense in prostate cancer

Abstract Lethal prostate cancer (PCa) is a genetically heterogeneous disease characterized by evolving androgen receptor (AR) signaling, eventually culminating in castration resistance. The tumor suppressor gene BRCA1 has multiple functions that include secondary processes cooperating with its main function as a caretaker of genomic integrity. BRCA1 is often mutated in breast and ovarian cancer, but BRCA1 mutations are also associated with PCa, although they are less frequently observed. Most PCa patients do not, however, carry BRCA1 mutations, and interestingly, it has been shown that BRCA1 expression is enriched in castration‐resistant PCa. In this study we elucidated the prostate tissue‐specific role of the BRCA1 protein. Although the regulation of DNA damage response genes has been studied in PCa, comprehensive analyses of BRCA1 regulation in the context of androgen signaling are lacking. Our results indicate that BRCA1 is dynamically regulated by AR signaling and that activation of AR via its natural ligand, dihydrotestosterone, represses BRCA1 expression. Our analyses both in vitro and of patient samples and mouse xenografts showed that BRCA1 expression was induced and sustained after androgen deprivation. Moreover, we observed that oxidative stress–related pathways were regulated by BRCA1 in PCa cells and that androgen deprivation therapy–induced activation of BRCA1 supported the function of NRF2, the master regulator of antioxidant defense, and a known interactor of BRCA1. Impaired NRF2 activity, in the absence of BRCA1, decreased growth in a 3D environment. Our findings shed light on the functional role of BRCA1 protein in PCa and suggest that BRCA1 is regulated by the evolving AR signaling state during PCa progression. Thus, AR‐mediated suppression of BRCA1 accumulates oncogenic alterations in the early phases of PCa tumor progression and safeguards from excessive reactive oxygen species (ROS) when upregulated during androgen deprivation therapy. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Mucinous cystic neoplasms of the pancreas and liver share a similar DNA methylation profile with mucinous ovarian tumors

Abstract The origin of mucinous cystic neoplasms (MCNs) remains a major challenge in hepato‐pancreato‐biliary pathology. These cystic tumors are defined by their mucinous epithelium and ovarian‐like stroma, with an estimated 10% risk of progression to invasive carcinoma. The origin of the ovarian‐like stroma remains a subject of debate. In this study, we conducted immunohistochemical profiling, targeted DNA sequencing, and genome‐wide DNA methylation analysis on a cohort of 15 pancreatic MCNs (MCN‐P) and six hepatic MCNs (MCN‐L). Using immunohistochemistry and targeted DNA sequencing, we unequivocally established the diagnosis of MCN. Unsupervised DNA methylation profile analysis of reference classes of pancreatic neoplasms (11 entities and normal pancreatic tissue from 224 unique samples) revealed that MCN‐P predominantly forms a distinct group. In the DNA methylation landscape of liver tumors, encompassing five tumor types and normal bile duct tissue from 136 unique samples, MCN‐L demonstrated a specific methylation profile when compared with all other entities. Furthermore, within the DNA methylation landscape of ovarian tumors – featuring five tumor types, normal Fallopian tube, and normal ovarian tissue from 90 unique samples – we found that both MCN‐P and MCN‐L grouped with mucinous ovarian carcinoma and mucinous borderline ovarian tumors (mBOTs). Notably, low‐grade MCNs exhibited greater DNA methylation similarities to mBOTs, while high‐grade or invasive MCNs were primarily associated with mucinous ovarian carcinomas. When analyzing all samples together (19 tumor types and four normal tissue types, n  = 430), MCNs similarly grouped with mucinous ovarian tumors and normal ovarian tissue. Additionally, in a network analysis of differentially methylated probes, MCN‐P and MCN‐L share significant methylation traits, closely resembling mucinous ovarian tumors. In conclusion, our findings highlight that MCN‐P and MCN‐L are distinct entities in the landscape of pancreatic and hepatic tumors and show DNA methylation profile similarities with mucinous ovarian tumors, suggesting a potential common origin. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Cellular origins of mucinous ovarian carcinoma

AbstractMucinous ovarian carcinoma (MOC) is a rare histotype of epithelial ovarian cancer. Its origins are obscure: while many mucinous tumours in the ovary are metastases from the gastrointestinal tract, MOC can occur as an ovarian primary; however, the cell of origin is not well established. In this review we summarise the pathological, epidemiological, and molecular evidence for the cellular origins of MOC. We propose a model for the origins of the various tumours of the ovary with mucinous differentiation. We distinguish Müllerian from gastrointestinal‐type mucinous differentiation. A small proportion of the latter arise from teratoma and a distinct terminology has been proposed. Other gastrointestinal mucinous tumours are associated with Brenner tumours and arise from their associated benign lesions, Walthard nests. The remaining mucinous tumours develop either through mucinous metaplasia in established Müllerian tumours or with even greater plasticity through gastrointestinal metaplasia of epithelial or mesothelial ovarian inclusions. This model remains to be validated and mechanistically understood and we discuss future research directions. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

The genomic trajectory of ovarian high‐grade serous carcinoma can be observed in STIC lesions

AbstractOvarian high‐grade serous carcinoma (HGSC) originates in the fallopian tube, with secretory cells carrying a TP53 mutation, known as p53 signatures, identified as potential precursors. p53 signatures evolve into serous tubal intraepithelial carcinoma (STIC) lesions, which in turn progress into invasive HGSC, which readily spreads to the ovary and disseminates around the peritoneal cavity. We recently investigated the genomic landscape of early‐ and late‐stage HGSC and found higher ploidy in late‐stage (median 3.1) than early‐stage (median 2.0) samples. Here, to explore whether the high ploidy and possible whole‐genome duplication (WGD) observed in late‐stage disease were determined early in the evolution of HGSC, we analysed archival formalin‐fixed paraffin‐embedded (FFPE) samples from five HGSC patients. p53 signatures and STIC lesions were laser‐capture microdissected and sequenced using shallow whole‐genome sequencing (sWGS), while invasive ovarian/fallopian tube and metastatic carcinoma samples underwent macrodissection and were profiled using both sWGS and targeted next‐generation sequencing. Results showed highly similar patterns of global copy number change between STIC lesions and invasive carcinoma samples within each patient. Ploidy changes were evident in STIC lesions, but not p53 signatures, and there was a strong correlation between ploidy in STIC lesions and invasive ovarian/fallopian tube and metastatic samples in each patient. The reconstruction of sample phylogeny for each patient from relative copy number indicated that high ploidy, when present, occurred early in the evolution of HGSC, which was further validated by copy number signatures in ovarian and metastatic tumours. These findings suggest that aberrant ploidy, suggestive of WGD, arises early in HGSC and is detected in STIC lesions, implying that the trajectory of HGSC may be determined at the earliest stages of tumour development. © 2024 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Genetic and epigenetic alterations in precursor lesions of endometrial endometrioid carcinoma

AbstractThe hyperplasia–carcinoma sequence is a stepwise tumourigenic programme towards endometrial cancer in which normal endometrial epithelium becomes neoplastic through non‐atypical endometrial hyperplasia (NAEH) and atypical endometrial hyperplasia (AEH), under the influence of unopposed oestrogen. NAEH and AEH are known to exhibit polyclonal and monoclonal cell growth, respectively; yet, aside from focal PTEN protein loss, the genetic and epigenetic alterations that occur during the cellular transition remain largely unknown. We sought to explore the potential molecular mechanisms that promote the NAEH–AEH transition and identify molecular markers that could help to differentiate between these two states. We conducted target‐panel sequencing on the coding exons of 596 genes, including 96 endometrial cancer driver genes, and DNA methylome microarrays for 48 NAEH and 44 AEH lesions that were separately collected via macro‐ or micro‐dissection from the endometrial tissues of 30 cases. Sequencing analyses revealed acquisition of the PTEN mutation and the clonal expansion of tumour cells in AEH samples. Further, across the transition, alterations to the DNA methylome were characterised by hypermethylation of promoter/enhancer regions and CpG islands, as well as hypo‐ and hyper‐methylation of DNA‐binding regions for transcription factors relevant to endometrial cell differentiation and/or tumourigenesis, including FOXA2, SOX17, and HAND2. The identified DNA methylation signature distinguishing NAEH and AEH lesions was reproducible in a validation cohort with modest discriminative capability. These findings not only support the concept that the transition from NAEH to AEH is an essential step within neoplastic cell transformation of endometrial epithelium but also provide deep insight into the molecular mechanism of the tumourigenic programme. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Causality and functional relevance of BRCA1 and BRCA2 pathogenic variants in non‐high‐grade serous ovarian carcinomas

Abstract The identification of causal BRCA1/2 pathogenic variants (PVs) in epithelial ovarian carcinoma (EOC) aids the selection of patients for genetic counselling and treatment decision‐making. Current recommendations therefore stress sequencing of all EOCs, regardless of histotype. Although it is recognised that BRCA1/2 PVs cluster in high‐grade serous ovarian carcinomas (HGSOC), this view is largely unsubstantiated by detailed analysis. Here, we aimed to analyse the results of BRCA1/2 tumour sequencing in a centrally revised, consecutive, prospective series including all EOC histotypes. Sequencing of n  = 946 EOCs revealed BRCA1/2 PVs in 125 samples (13%), only eight of which were found in non‐HGSOC histotypes. Specifically, BRCA1/2 PVs were identified in high‐grade endometrioid (3/20; 15%), low‐grade endometrioid (1/40; 2.5%), low‐grade serous (3/67; 4.5%), and clear cell (1/64; 1.6%) EOCs. No PVs were identified in any mucinous ovarian carcinomas tested. By re‐evaluation and using loss of heterozygosity and homologous recombination deficiency analyses, we then assessed: (1) whether the eight ‘anomalous’ cases were potentially histologically misclassified and (2) whether the identified variants were likely causal in carcinogenesis. The first ‘anomalous’ non‐HGSOC with a BRCA1/2 PV proved to be a misdiagnosed HGSOC. Next, germline BRCA2 variants, found in two p53‐abnormal high‐grade endometrioid tumours, showed substantial evidence supporting causality. One additional, likely causal variant, found in a p53‐wildtype low‐grade serous ovarian carcinoma, was of somatic origin. The remaining cases showed retention of the BRCA1/2 wildtype allele, suggestive of non‐causal secondary passenger variants. We conclude that likely causal BRCA1/2 variants are present in high‐grade endometrioid tumours but are absent from the other EOC histotypes tested. Although the findings require validation, these results seem to justify a transition from universal to histotype‐directed sequencing. Furthermore, in‐depth functional analysis of tumours harbouring BRCA1/2 variants combined with detailed revision of cancer histotypes can serve as a model in other BRCA1/2 ‐related cancers. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

The unique metabolome of clear cell ovarian carcinoma

AbstractClear cell ovarian carcinoma (CCOC) is an aggressive malignancy affecting younger women. Despite ovarian cancer subtypes having diverse molecular and clinical characteristics, the mainstay of treatment for advanced stage disease remains cytotoxic chemotherapy. Late stage CCOC is resistant to conventional chemotherapy, which means a suboptimal outcome for patients affected. Despite detailed genomic, epigenomic, transcriptomic, and proteomic characterisation, subtype‐specific treatment for CCOC has shown little progress. The unique glycogen accumulation defining CCOC suggests altered metabolic pathway activity and dependency. This study presents the first metabolomic landscape of ovarian cancer subtypes, including 42 CCOC, 20 high‐grade serous and 21 endometrioid ovarian carcinomas, together comprising the three most common ovarian carcinoma subtypes. We describe a distinct metabolomic landscape of CCOC compared with other ovarian cancer subtypes, including alterations in energy utilisation and cysteine metabolism. In addition, we identify CCOC‐specific alterations in metabolic pathways including serine biosynthesis and ROS‐associated pathways that could serve as potential therapeutic targets. Our study provides the first in‐depth study into the metabolome of ovarian cancers and a rich resource to support ongoing research efforts to identify subtype‐specific therapeutic targets that could improve the dismal outcome for patients with this devastating malignancy. © 2024 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Activated immune infiltrates expand opportunities for targeted therapy in p53‐abnormal endometrial carcinoma

AbstractTumor protein p53 mutated/abnormal (p53abn) endometrial carcinomas account for over 50% of deaths but comprise only 15% of all endometrial carcinomas. Most patients show limited response to standard‐of‐care chemotherapy with or without radiotherapy, and only a minority of cases are amenable to targeted therapies like poly‐ADP ribose polymerase (PARP) inhibitors and HER2‐directed therapies. Recent immunotherapy clinical trials have demonstrated remarkable efficacy, not only in mismatch repair deficient (MMRd) tumors but also in a subset of mismatch repair‐proficient (MMRp) tumors. However, the immune microenvironment and its relationship to other therapeutic targets in MMRp endometrial carcinoma remains poorly understood. Here, we characterize the immune microenvironment of p53abn endometrial carcinoma, the most clinically aggressive subtype of MMRp endometrial carcinoma, and correlate antitumor immune signatures with other targetable alterations. We accrued 256 treatment‐naïve p53abn endometrial carcinomas and systemically profiled T‐cell, B‐cell, myeloid, and tumor‐cell populations with multiplex immunofluorescence to assess the tissue localization and functional status of immune cells. Shallow whole‐genome sequencing was performed on a subset of 126 cases. Patterns of immune infiltration were compared to survival outcomes and mutational signatures. Mixture modeling divided p53abn endometrial carcinoma into tumor‐infiltrating lymphocyte (TIL)‐rich and TIL‐poor subsets. Over 50% of tumors were TIL‐rich. TIL‐rich cases overexpressed targetable immune evasion molecules and were associated with longer overall and disease‐specific survival in multivariate analysis. This effect was particularly pronounced in advanced stage disease and in patients who did not receive adjuvant chemotherapy. TIL did not associate with homologous recombination deficient mutational signatures or HER2 amplification. Our findings demonstrate a biological rationale for immunotherapy in a substantial subset of patients with p53abn endometrial cancer and may help inform combination therapies with immune checkpoint inhibition, PARP inhibitors, and anti‐HER2 agents. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Mesonephric‐like adenocarcinoma harbours characteristic copy number variations and a distinct DNA methylation signature closely related to mesonephric adenocarcinoma of the cervix

Abstract Mesonephric‐like adenocarcinoma (MLA) of the female genital tract is an uncommon histotype that can arise in both the endometrium and the ovary. The exact cell of origin and histogenesis currently remain unknown. Here, we investigated whole genome DNA methylation patterns and copy number variations (CNVs) in a series of MLAs in the context of a large cohort of various gynaecological carcinoma types. CNV analysis of 19 MLAs uncovered gains of chromosomes 1q (18/19, 95%), 10 (15/19, 79%), 12 (14/19, 74%), and 2 (10/19, 53%), as well as loss of chromosome 1p (7/19, 37%). Gains of chromosomes 1q, 10, and 12 were also identified in the majority of mesonephric adenocarcinomas of the uterine cervix (MAs) as well as subsets of endometrioid carcinomas (ECs) and low‐grade serous carcinomas of the ovary (LGSCs) but only in a minority of serous carcinomas of the uterine corpus (USCs), clear cell carcinomas (CCCs), and tubo‐ovarian high‐grade serous carcinomas (HGSCs). While losses of chromosome 1p together with gains of chromosome 1q were also identified in both MA and LGSC, gains of chromosome 2 were almost exclusively identified in MLA and MA. Unsupervised hierarchical clustering and t‐SNE analysis of DNA methylation data (Illumina EPIC array) identified a co‐clustering for MLAs and MAs, which was distinct from clusters of ECs, USCs, CCCs, LGSCs, and HGSCs. Group‐wise comparisons confirmed a close epigenetic relationship between MLA and MA. These findings, in conjunction with the established histological and immunophenotypical overlap, suggest bona fide mesonephric differentiation, and support a more precise terminology of mesonephric‐type adenocarcinoma instead of MLA in these tumours. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

The association between the tumor immune microenvironments and clinical outcome in low‐grade, early‐stage endometrial cancer patients

AbstractEndometrial tumors show substantial heterogeneity in their immune microenvironment. This heterogeneity could be used to improve the accuracy of current outcome prediction tools. We assessed the immune microenvironment of 235 patients diagnosed with low‐grade, early‐stage endometrial cancer. Multiplex quantitative immunofluorescence was carried out to measure CD8, CD68, FOXP3, PD‐1, and PD‐L1 markers, as well as cytokeratin (CK), on tissue microarrays. Clustering results revealed five robust immune response patterns, each associated with specific immune populations, cell phenotypes, and cell spatial clustering. Most samples (69%) belonged to the immune‐desert subtype, characterized by low immune cell densities. Tumor‐infiltrating lymphocyte (TIL)‐rich samples (4%) displayed high CD8+ T‐cell infiltration, as well as a high percentage of CD8/PD‐1+ cells. Immune‐exclusion samples (19%) displayed the lowest CD8+ infiltration combined with high PD‐L1 expression levels in CK+ tumor cells. In addition, they demonstrated high tumor cell spatial clustering as well as increased spatial proximity of CD8+/PD‐1+ and CK/PD‐L1+ cells. FOXP3 and macrophage‐rich phenotypes (3% and 4% of total samples) displayed relatively high levels of FOXP3+ regulatory T‐cells and CD68+ macrophages, respectively. These phenotypes correlated with clinical outcomes, with immune‐exclusion tumors showing an association with tumor relapse. When compared with prediction models built using routine pathological variables, models optimized with immune variables showed increased outcome prediction capacity (AUC = 0.89 versus 0.78) and stratification potential. The improved prediction capacity was independent of mismatch repair protein status and adjuvant radiotherapy treatment. Further, immunofluorescence results could be partially recapitulated using single‐marker immunohistochemistry (IHC) performed on whole tissue sections. TIL‐rich tumors demonstrated increased CD8+ T‐cells by IHC, while immune‐exclusion tumors displayed a lack of CD8+ T‐cells and frequent expression of PD‐L1 in tumor cells. Our results demonstrate the capability of the immune microenvironment to improve standard prediction tools in low‐grade, early‐stage endometrial carcinomas. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Serial genomic analysis of endometrium supports the existence of histologically indistinct endometrial cancer precursors

The endometrium is unique as an accessible anatomic location that can be repeatedly biopsied and where diagnostic biopsies do not extirpate neoplastic lesions. We exploited these features to retrospectively characterize serial genomic alterations along the precancer/cancer continuum in individual women. Cases were selected based on (1) endometrial cancer diagnosis/hysterectomy and (2) preceding serial endometrial biopsies including for some patients an early biopsy before a precancer histologic diagnosis. A comprehensive panel was designed for endometrial cancer genes. Formalin-fixed, paraffin-embedded specimens for each cancer, preceding biopsies, and matched germline samples were subjected to barcoded high-throughput sequencing to identify mutations and track their origin and allelic frequency progression. In total, 92 samples from 21 patients were analyzed, providing an opportunity for new insights into early endometrial cancer progression. Definitive invasive endometrial cancers exhibited expected mutational spectra, and canonical driver mutations were detectable in preceding biopsies. Notably, ≥1 cancer mutations were detected prior to the histopathologic diagnosis of an endometrial precancer in the majority of patients. In 18/21 cases, ≥1 mutations were confirmed by abnormal protein levels or subcellular localization by immunohistochemistry, confirming genomic data and providing unique views of histologic correlates. In 19 control endometria, mutation counts were lower, with a lack of canonical endometrial cancer hotspot mutations. Our study documents the existence of endometrial lesions that are histologically indistinct but are bona fide endometrial cancer precursors. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Definitive study shows no association between ARID1A mutation status and clinical outcome in endometriosis‐related ovarian cancers‡

AbstractThe ARID1A tumour suppressor protein is a component of the SWI/SNF chromatin remodelling complex, which is mutated in approximately 20% of all human cancers. ARID1A mutational status is considered to hold prognostic significance in a range of solid malignancies, yet in endometriosis‐related ovarian carcinomas there has been a lack of clarity of its prognostic role. Moreover, the relationship between ARID1A status and immune infiltrate is also poorly understood. In a recent issue of The Journal of Pathology, a large comprehensive study by Heinze, Nazeran et al addressed these areas by reviewing 1,623 endometriosis‐associated ovarian carcinomas and correlating ARID1A status using standardised immunohistochemistry to infer mutation status, with comprehensive clinicopathological features, mismatch repair status and CD8+ tumour infiltrating lymphocytes. The study definitively showed that ARID1A status does not provide any independent prognostic value in endometriosis‐associated ovarian carcinomas. ARID1A loss was, however, shown to be associated with mismatch repair deficiency and increased CD8+ tumour infiltrating lymphocytes in endometrioid ovarian carcinoma, which may be relevant for future studies. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Discordant prognosis of mismatch repair deficiency in colorectal and endometrial cancer reflects variation in antitumour immune response and immune escape

AbstractDefective DNA mismatch repair (dMMR) causes elevated tumour mutational burden (TMB) and microsatellite instability (MSI) in multiple cancer types. dMMR/MSI colorectal cancers (CRCs) have enhanced T‐cell infiltrate and favourable outcome; however, this association has not been reliably detected in other tumour types, including endometrial cancer (EC). We sought to confirm this and explore the underpinning mechanisms. We first meta‐analysed CRC and EC trials that have examined the prognostic value of dMMR/MSI and confirmed that dMMR/MSI predicts better prognosis in CRC, but not EC, with statistically significant variation between cancers (hazard ratio [HR] = 0.63, 95% confidence interval [CI] = 0.54–0.73 versus HR = 1.15, 95% CI = 0.72–1.58; PINT = 0.02). Next, we studied intratumoural immune infiltrate in CRCs and ECs of defined MMR status and found that while dMMR was associated with increased density of tumour‐infiltrating CD3+ and CD8+ T‐cells in both cancer types, the increases were substantially greater in CRC and significant only in this group (PINT = 4.3e‐04 and 7.3e‐03, respectively). Analysis of CRC and EC from the independent Cancer Genome Atlas (TCGA) series revealed similar variation and significant interactions in proportions of tumour‐infiltrating lymphocytes, CD8+, CD4+, NK cells and immune checkpoint expression, confirming a more vigorous immune response to dMMR/MSI in CRC than EC. Agnostic analysis identified the IFNγ pathway activity as strongly upregulated by dMMR/MSI in CRC, but downregulated in EC by frequent JAK1 mutations, the impact of which on IFNγ response was confirmed by functional analyses. Collectively, our results confirm the discordant prognosis of dMMR/MSI in CRC and EC and suggest that this relates to differences in intratumoural immune infiltrate and tumour genome. Our study underscores the need for tissue‐specific analysis of cancer biomarkers and may help inform immunotherapy use. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Cellular context determines DNA methylation profiles in SWI/SNF‐deficient cancers of the gynecologic tract

AbstractSWI/SNF (SWItch/Sucrose Non‐Fermentable) complex deficiency has been reported in a wide variety of cancers and is often associated with an undifferentiated phenotype. In the gynecologic tract SWI/SNF‐deficient cancers are diagnostically challenging and little is known about their cellular origins. Here we show that undifferentiated endometrial carcinoma (UDEC), SMARCA4‐deficient uterine sarcoma (SDUS), and ovarian small cell carcinoma, hypercalcemic type (SCCOHT) harbor distinct DNA methylation signatures despite shared morphology and SWI/SNF inactivation. Our results indicate that the cellular context is an important determinant of the epigenetic landscape, even in the setting of core SWI/SNF deficiency, and therefore methylation profiling may represent a useful diagnostic tool in undifferentiated, SWI/SNF‐deficient cancers. Furthermore, applying copy number analyses and group‐wise differential methylation analyses including endometrioid endometrial carcinomas and extracranial malignant rhabdoid tumors, we uncover analogous molecular features in SDUS and SCCOHT in contrast to UDEC. These results suggest that SDUS and SCCOHT represent chromosomally stable SWI/SNF‐deficient cancers of the gynecologic tract, which are within the broader spectrum of malignant rhabdoid tumors. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Clinicopathological and molecular characterisation of ‘multiple‐classifier’ endometrial carcinomas

AbstractEndometrial carcinoma (EC) molecular classification based on four molecular subclasses identified in The Cancer Genome Atlas (TCGA) has gained relevance in recent years due to its prognostic utility and potential to predict benefit from adjuvant treatment. While most ECs can be classified based on a single classifier (POLE exonuclease domain mutations – POLEmut, MMR deficiency – MMRd, p53 abnormal – p53abn), a small but clinically relevant group of tumours harbour more than one molecular classifying feature and are referred to as ‘multiple‐classifier’ ECs. We aimed to describe the clinicopathological and molecular features of multiple‐classifier ECs with abnormal p53 (p53abn). Within a cohort of 3518 molecularly profiled ECs, 107 (3%) tumours displayed p53abn in addition to another classifier(s), including 64 with MMRd (MMRd–p53abn), 31 with POLEmut (POLEmut–p53abn), and 12 with all three aberrations (MMRd–POLEmut–p53abn). MMRd–p53abn ECs and POLEmut–p53abn ECs were mostly grade 3 endometrioid ECs, early stage, and frequently showed morphological features characteristic of MMRd or POLEmut ECs. 18/28 (60%) MMRd–p53abn ECs and 7/15 (46.7%) POLEmut–p53abn ECs showed subclonal p53 overexpression, suggesting that TP53 mutation was a secondary event acquired during tumour progression. Hierarchical clustering of TCGA ECs by single nucleotide variant (SNV) type and somatic copy number alterations (SCNAs) revealed that MMRd–p53abn tumours mostly clustered with single‐classifier MMRd tumours (20/23) rather than single‐classifier p53abn tumours (3/23), while POLEmut–p53abn tumours mostly clustered with single‐classifier POLEmut tumours (12/13) and seldom with single‐classifier p53abn tumours (1/13) (both p ≤ 0.001, chi‐squared test). Finally, the clinical outcome of patients with MMRd–p53abn and POLEmut–p53abn ECs [stage I 5‐year recurrence‐free survival (RFS) of 92.2% and 94.1%, respectively] was significantly different from single‐classifier p53abn EC (stage I RFS 70.8%, p = 0.024 and p = 0.050, respectively). Our results support the classification of MMRd–p53abn EC as MMRd and POLEmut–p53abn EC as POLEmut. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Interpretation of somatic POLE mutations in endometrial carcinoma

AbstractPathogenic somatic missense mutations within the DNA polymerase epsilon (POLE) exonuclease domain define the important subtype of ultramutated tumours (‘POLE‐ultramutated’) within the novel molecular classification of endometrial carcinoma (EC). However, clinical implementation of this classifier requires systematic evaluation of the pathogenicity of POLE mutations. To address this, we examined base changes, tumour mutational burden (TMB), DNA microsatellite instability (MSI) status, POLE variant frequency, and the results from six in silico tools on 82 ECs with whole‐exome sequencing from The Cancer Genome Atlas (TCGA). Of these, 41 had one of five known pathogenic POLE exonuclease domain mutations (EDM) and showed characteristic genomic alterations: C>A substitution > 20%, T>G substitutions > 4%, C>G substitutions < 0.6%, indels < 5%, TMB > 100 mut/Mb. A scoring system to assess these alterations (POLE‐score) was developed; based on their scores, 7/18 (39%) additional tumours with EDM were classified as POLE‐ultramutated ECs, and the six POLE mutations present in these tumours were considered pathogenic. Only 1/23 (4%) tumours with non‐EDM showed these genomic alterations, indicating that a large majority of mutations outside the exonuclease domain are not pathogenic. The infrequent combination of MSI‐H with POLE EDM led us to investigate the clinical significance of this association. Tumours with pathogenic POLE EDM co‐existent with MSI‐H showed genomic alterations characteristic of POLE‐ultramutated ECs. In a pooled analysis of 3361 ECs, 13 ECs with DNA mismatch repair deficiency (MMRd)/MSI‐H and a pathogenic POLE EDM had a 5‐year recurrence‐free survival (RFS) of 92.3%, comparable to previously reported POLE‐ultramutated ECs. Additionally, 14 cases with non‐pathogenic POLE EDM and MMRd/MSI‐H had a 5‐year RFS of 76.2%, similar to MMRd/MSI‐H, POLE wild‐type ECs, suggesting that these should be categorised as MMRd, rather than POLE‐ultramutated ECs for prognostication. This work provides guidance on classification of ECs with POLE mutations, facilitating implementation of POLE testing in routine clinical care. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Spatial analysis of HPV ‐associated cervical intraepithelial neoplastic tissues demonstrate distinct immune signatures associated with cervical cancer progression

Abstract Cervical cancer remains the fourth most common cancer affecting women worldwide, and incidences of other HPV‐related cancers continue to rise. For the development of effective prevention strategies in high‐risk patients, we aimed to better understand the roles of inflammatory pathways and the tumour microenvironment as the main driver of progression to malignancy in HPV‐infected tissues. We analysed the spatial organisation of seven samples of HPV+ high‐grade squamous intraepithelial lesion (HSIL) and cervical intraepithelial neoplasia 3 (CIN3), comparing tumour heterogeneity and immune microenvironments between premalignant (neoplastic) and adjacent cervical tissues. We observed evidence of immune suppression within the neoplastic regions across all samples and identified distinct immune clusters for each dysplastic lesion. Previous single‐cell data analyses in an HPV16 E7 oncoprotein‐driven transgenic mouse model suggested a potential role for IL34‐CSF1R signalling in immune modulation, where low IL34 expression was associated with Langerhans cell dysfunction, and, in cervical cancer, with poor patient outcome. Here we observed that IL34‐CSF1R coexpression was absent within HPV‐associated neoplastic regions, but present in adjacent normal tissue regions. Additionally, we identified enrichment of an M2 gene signature in neoplastic regions, while adjacent tissue was enriched with a proinflammatory M1 gene signature. Our findings provide biopathological insights into the spatial cellular and molecular mechanisms underlying HPV‐associated cervical cancer immune regulation and suggest a strategy to modulate the immune system in HPV‐positive neoplastic cervical and other tissues. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Genomic characterization and histologic analysis of uterine leiomyosarcoma arising from leiomyoma with bizarre nuclei

Abstract Leiomyoma with bizarre nuclei (LM‐BN) is a rare variant of leiomyoma with a benign clinical course. In contrast, leiomyosarcoma (LMS) is a high‐grade, malignant neoplasm characterized by high recurrence rates and poor survival. While LM‐BN and LMS show distinct morphologies, they share similar immunoprofiles and molecular alterations, with both considered ‘genomically unstable’. Rare cases of LM‐BN associated with LMS have been reported; however, the histogenesis and molecular relationship between these two tumors remains unclear. In this study, we assessed 11 cases of LMS arising in conjunction with LM‐BN confirmed by histology and immunohistochemistry (IHC), further analyzed by clinical, histologic, and molecular characteristics of these distinct components. LM‐BN and LMS had similar p16 and p53 IHC patterns, but LMS had a higher Ki‐67 index and lower estrogen and progesterone eceptor expression. Digital image analysis based on cytologic features revealed spatial relationships between LMS and LM‐BN. Genomic copy number alterations (CNAs) demonstrated the same clonal origin of LMS arising from existing LM‐BN through conserved CNAs. LMS harbored highly complex CNAs and more frequent losses of the TP53 , RB1 , and PTEN genomic regions than LM‐BN ( p  = 0.0031), with CDKN2A/B deletion identified in LMS only. Mutational profiling revealed many shared oncogenic alterations in both LM‐BN and LMS; however, additional mutations were present within LMS, indicative of tumor progression through progressive genomic instability. Analysis of spatial transcriptomes defined uniquely expressed gene signatures that matched the geographic distribution of LM‐BN, LMS, and other cell types. Our findings indicate for the first time that a subset of LMS arises from an existing LM‐BN, and highly complex genomic alterations could be potential high risks associated with disease progression in LM‐BN. © 2024 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

PAX2 is regulated by estrogen/progesterone through promoter methylation in endometrioid adenocarcinoma and has an important role in carcinogenesis via the AKT / mTOR signaling pathway

Abstract Endometrioid adenocarcinoma (EEC) is one of the most common cancers of the female reproductive system. In recent years, much emphasis has been placed on early diagnosis and treatment. PAX2 (Paired box 2) inactivation is reportedly an important biomarker for endometrioid intraepithelial neoplasia (EIN) and EEC. However, the role of PAX2 in EEC carcinogenesis remains unclear. PAX2 expression and associated clinical characteristics were analyzed via The Cancer Genome Atlas, Gene Expression Omnibus, and Cancer Cell Line Encyclopedia databases and clinical paired EIN/EEC tissue samples. Bioinformatic analysis was conducted to identify the putative molecular function and mechanism of PAX2. Cell proliferation, colony formation, cell migration, and invasion assays in vitro , and mouse xenograft models were utilized to study the biological functions of PAX2 in vivo . Pyrosequencing and the demethylating drug 5‐Aza‐dc were used to verify promoter methylation in clinical tissues and cell lines, respectively. The mechanism underlying the regulatory effect of estrogen (E2) and progesterone (P4) on PAX2 expression was investigated by receptor block assay and double luciferase reporter assay. PAX2 expression was found to be significantly downregulated in EIN and EEC tissues, its overexpression inhibited EEC cell malignant behaviors in vivo and in vitro and inhibited the AKT/mTOR signaling pathway. PAX2 inactivation in EEC was related to promoter methylation, and its expression was regulated by E2 and P4 through their receptors via promoter methylation. Our findings elucidated the expression and function of PAX2 in EEC and have provided hitherto undocumented evidence of the underlying molecular mechanisms. PAX2 expression is suppressed by estrogen prompting its methylation through estrogen receptor. Furthermore, PAX2 regulates the AKT/mTOR signaling pathway to influence EEC progression. © 2024 The Pathological Society of Great Britain and Ireland.

Oncogenic BRAF and KRAS mutations in endosalpingiosis

AbstractEndosalpingiosis, a microscopic lesion composed of ectopic Fallopian tube epithelium, frequently involves the peritoneum and lymph nodes in patients with ovarian serous borderline tumour or low‐grade serous carcinoma, but its pathogenic significance remains unclear. Using laser‐capture microdissection and droplet digital PCR, we investigated whether endosalpingiosis harbours the driver mutations in BRAF and KRAS that characterise ovarian low‐grade serous neoplasms. Somatic mutations were detected in 14 (33%) of 43 endosalpingiotic lesions analysed. Of 21 women with endosalpingiosis associated with a synchronous or metachronous ovarian low‐grade serous tumour, mutations were identified in endosalpingiotic lesions from 11 (52%) women, with most cases (10/11, 91%) demonstrating identical mutations in both tumour and endosalpingiosis. In contrast, of 13 cases of endosalpingiosis not associated with an ovarian tumour, only one harboured a KRAS mutation. The proliferative activity as assessed by Ki‐67 immunohistochemistry was lower in endosalpingiosis than in low‐grade serous tumours, and endosalpingiosis with either a BRAF or KRAS mutation had a significantly lower Ki‐67 index than those without. Ectopic expression of KRASG12V in Fallopian tube epithelial cells led to ERK phosphorylation, p21 induction, growth arrest and cellular senescence. In conclusion, we demonstrate that endosalpingiosis represents an interesting example of cancer driver mutations in deceptively normal‐appearing cells, which may be prone to neoplastic transformation upon bypass of endogenous oncosuppressive mechanisms. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

ALDH1A1‐related stemness in high‐grade serous ovarian cancer is a negative prognostic indicator but potentially targetable by EGFR/mTOR‐PI3K/aurora kinase inhibitors

AbstractPoor chemotherapy response remains a major treatment challenge for high‐grade serous ovarian cancer (HGSC). Cancer stem cells are the major contributors to relapse and treatment failure as they can survive conventional therapy. Our objectives were to characterise stemness features in primary patient‐derived cell lines, correlate stemness markers with clinical outcome and test the response of our cells to both conventional and exploratory drugs. Tissue and ascites samples, treatment‐naive and/or after neoadjuvant chemotherapy, were prospectively collected. Primary cancer cells, cultured under conditions favouring either adherent or spheroid growth, were tested for stemness markers; the same markers were analysed in tissue and correlated with chemotherapy response and survival. Drug sensitivity and resistance testing was performed with 306 oncology compounds. Spheroid growth condition HGSC cells showed increased stemness marker expression (including aldehyde dehydrogenase isoform I; ALDH1A1) as compared with adherent growth condition cells, and increased resistance to platinum and taxane. A set of eight stemness markers separated treatment‐naive tumours into two clusters and identified a distinct subgroup of HGSC with enriched stemness features. Expression of ALDH1A1, but not most other stemness markers, was increased after neoadjuvant chemotherapy and its expression in treatment‐naive tumours correlated with chemoresistance and reduced survival. In drug sensitivity and resistance testing, five compounds, including two PI3K‐mTOR inhibitors, demonstrated significant activity in both cell culture conditions. Thirteen compounds, including EGFR, PI3K‐mTOR and aurora kinase inhibitors, were more toxic to spheroid cells than adherent cells. Our results identify stemness markers in HGSC that are associated with a decreased response to conventional chemotherapy and reduced survival if expressed by treatment‐naive tumours. EGFR, mTOR‐PI3K and aurora kinase inhibitors are candidates for targeting this cell population. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

SWI/SNF‐deficient undifferentiated malignancies: where to draw the line†

AbstractAlterations in chromatin remodelling genes are increasingly recognised as drivers of undifferentiated malignancies. In atypical teratoid/rhabdoid tumours (ATRTs) and extracranial rhabdoid tumours (ECRTs), inactivation of SMARCB1 underlies >95% of cases. In the remainder, the culprit is another SWI/SNF family member, SMARCA4. By contrast, in small cell carcinoma of the ovary hypercalcaemic type (SCCOHT), SMARCA4 deficiency is by far the most common driver mechanism, while SMARCB1 alterations are rarely seen. It is unclear why alterations are so heavily weighted towards one or another subunit based on site alone, but both have become essential markers for the diagnosis and management of these undifferentiated lesions. Core SMARCA4‐deficient undifferentiated malignancies share an aggressive clinical course and show an overlapping morphologic phenotype. In their study, Andrianteranagna, Cyrta and colleagues used DNA methylation and gene expression profiling to compare two subsets of SMARCA4‐deficient malignancies diagnosed as SCCOHT and ECRT. Their work gives further insight into the subtle molecular spectrum of SMARCA4‐deficient tumours, and their distinction from ATRT and ECRT with SMARCB1 inactivation. The characterisation of these molecular features is likely to play an important role in the future as we try to establish a clinically meaningful framework for the diagnosis and management of these lesions. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

FOXL2C134W: much ado about something!†

AbstractRecent studies have suggested that the unique FOXL2C134W mutation, which is pathognomonic for adult granulosa cell tumours of the ovary, is a tumour suppressor gene. In a recent issue of The Journal of Pathology, a detailed study by Pilsworth et al seeks to rebut the proposition that the FOXL2C134W mutation, which uniquely characterises adult granulosa cell tumours of the ovary, leads to reduced transcript levels with the implication that FOXL2 is a tumour suppressor gene. The study provides compelling evidence that both wild‐type and mutant FOXL2 transcripts and protein are expressed at equivalent levels. In the context of other recent studies, one is drawn to the conclusion that FOXL2C134W is a gain‐of‐function mutation whose impact is mediated through enhanced interactions with the SMAD transcription factor complex. © 2021 The Pathological Society of Great Britain and Ireland.

FOXL2 in adult‐type granulosa cell tumour of the ovary: oncogene or tumour suppressor gene?

AbstractA recurrent mutation in FOXL2 (c.402C>G; p.C134W) is present in over 95% of adult‐type granulosa cell tumours (AGCTs). In contrast, various loss‐of‐function mutations in FOXL2 lead to the development of blepharophimosis, ptosis, and epicanthus inversus syndrome (BPES). BPES is characterised by an eyelid malformation often accompanied with primary ovarian insufficiency. Two recent studies suggest that FOXL2 C402G is a gain‐ or change‐of‐function mutation with altered DNA‐binding specificity. Another study proposes that FOXL2 C402G is selectively targeted for degradation, inducing somatic haploinsufficiency, suggesting its role as a tumour suppressor. The latter study relies on data indicative of an FOXL2 allelic imbalance in AGCTs. Here we present RNA‐seq data as genetic evidence that no real allelic imbalance is observed at the transcriptomic level in AGCTs. Additionally, there is no loss of protein expression in tumours harbouring the mutated allele. These data and other features of this mutation compared to other oncogenes and tumour suppressor genes argue strongly against FOXL2 being a tumour suppressor in this context. Given the likelihood that FOXL2 C402G is oncogenic, targeting the variant protein or its downstream consequences is the most viable path forward to identifying an effective treatment for this cancer. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Probing the tumorigenic potential of genetic interactions reconstituted in murine fallopian tube organoids

AbstractGenetically engineered mice have been the gold standard in modeling tumor development. Recent studies have demonstrated that genetically engineered organoids can develop subcutaneous tumors in immunocompromised mice, at least for organs that prefer predominant driver mutations for tumorigenesis. To further substantiate this concept, the fallopian tube (FT), a major cell of origin of ovarian high‐grade serous carcinoma (HGSC), which almost invariably carries TP53 mutations, was investigated for p53 inactivation‐driven tumorigenesis. Murine FT organoids subjected to lentiviral Cre‐mediated Trp53 deletion did not develop tumors. However, subsequent suppression of Pten and simultaneous induction of mutant Pik3ca led to the development of carcinoma in situ and HGSC‐like tumors, respectively, whereas concurrent deletion of Apc resulted in the development of benign cysts, mirroring frequent activation of the PI3K/AKT axis and the marginal impact of Wnt pathway activation in HGSC. Consistent with the frequent activation of the RAS pathway in HGSC, mutant Kras cooperated with Trp53 deletion for the development of tumors, which unexpectedly contained sarcoma cells in addition to carcinoma cells, despite the epithelial origin of the inoculated organoids. This finding is in sharp contrast with the exclusive adenocarcinoma development from gastrointestinal organoids with the same genotype reported in previous studies, suggesting a tissue‐specific epithelial–mesenchymal transition program. In tumor‐derived organoids, the Cre‐mediated recombination rate reached 100% for Trp53 but not for the other genes, highlighting the advantage of p53 inactivation in FT tumorigenesis. The Trp53 wildtype FT organoids expressing the mutant Kras developed sarcoma and carcinoma upon Cdkn2a suppression and Tgfbr2 deletion, respectively, revealing novel pro‐tumorigenic genetic cooperation and critical roles of TGF‐β signaling for epithelial–mesenchymal transition in FT‐derived tumorigenesis. Collectively, the organoid‐based approach represents a shortcut to tumorigenesis and provides novel insights into the relationships among genotype, cell type, and tumor phenotype underlying tumorigenesis. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

SMARCA4 ‐deficient rhabdoid tumours show intermediate molecular features between SMARCB1 ‐deficient rhabdoid tumours and small cell carcinomas of the ovary, hypercalcaemic type

Abstract Extracranial rhabdoid tumours (ECRTs) are an aggressive malignancy of infancy and early childhood. The vast majority of cases demonstrate inactivation of SMARCB1 (ECRT SMARCB1 ) on a background of a remarkably stable genome, a low mutational burden, and no other recurrent mutations. Rarely, ECRTs can harbour the alternative inactivation of SMARCA4 (ECRT SMARCA4 ) instead of SMARCB1. However, very few ECRT SMARCA4 cases have been published to date, and a systematic characterization of ECRT SMARCA4 is missing from the literature. In this study, we report the clinical, pathological, and genomic features of additional cases of ECRT SMARCA4 and show that they are comparable to those of ECRT SMARCB1. We also assess whether ECRT SMARCB1 , ECRT SMARCA4 , and small cell carcinomas of the ovary, hypercalcaemic type (SCCOHT) represent distinct or overlapping entities at a molecular level. Using DNA methylation and transcriptomics‐based tumour classification approaches, we demonstrate that ECRT SMARCA4 display molecular features intermediate between SCCOHT and ECRT SMARCB1 ; however, ECRT SMARCA4 appear to be more closely related to SCCOHT by DNA methylation. Conversely, both transcriptomics and DNA methylation show a larger gap between SCCOHT and ECRT SMARCB1 , potentially supporting their continuous separate classification. Lastly, we show that ECRT SMARCA4 display concomitant lack of SMARCA4 (BRG1) and SMARCA2 (BRM) expression at the protein level, similar to what is seen in SCCOHT. Overall, these results expand our knowledge on this rare tumour type and explore the similarities and differences among entities from the ‘rhabdoid tumour’ spectrum. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Methylation profile of imprinted genes provides evidence for teratomatous origin of a subset of mucinous ovarian tumours

Abstract Mucinous ovarian tumours are sometimes associated with mature teratomas. It is suggested that the mucinous tumours in this setting are derived from teratomas, but there remains the possibility of collision or metastasis from extra‐ovarian sites. Because mature ovarian teratomas are considered to be parthenogenetic tumours that arise from a single oocyte/ovum, they have only a maternal genome and therefore show maternal genome imprinting. If mucinous ovarian tumours originate from teratomas, their genome imprinting is theoretically maternal. One of the most important mechanisms of genome imprinting is DNA methylation. In the present study, we analysed a total of 28 mucinous ovarian tumours (7 with teratomas, 21 without teratomas; 14 malignant, 14 borderline) to clarify the methylation profiles of their imprinted genes using methylation‐specific multiplex ligation‐dependent probe amplification (MS‐MLPA) of 21 imprinting control regions (ICRs) of nine imprinted genes/gene clusters using formalin‐fixed, paraffin‐embedded samples. All cases lacked evidence of an extra‐ovarian primary mucinous tumour. In all seven mucinous tumours with teratomas, the overall methylation profile of mucinous tumours was comparable to that of teratomas, although some ICRs showed aberrant methylation. In contrast, all but one of the mucinous tumours without teratomas showed somatic or irregular methylation patterns. Morphologically, there was little teratomatous tissue in some mucinous tumours carrying teratoma‐type methylation profiles, suggesting that mucinous tumours overwhelmed ancestral teratomas. In conclusion, the methylation profile of imprinted genes provides evidence that a subset of mucinous ovarian tumours originated from mature teratomas. Genome imprinting‐based analysis is a promising strategy to verify the teratomatous origin of human tumours. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The proteome of clear cell ovarian carcinoma

AbstractClear cell ovarian carcinoma (CCOC) is the second most common subtype of epithelial ovarian carcinoma. Late‐stage CCOC is not responsive to gold‐standard chemotherapy and results in suboptimal outcomes for patients. In‐depth molecular insight is urgently needed to stratify the disease and drive therapeutic development. We conducted global proteomics for 192 cases of CCOC and compared these with other epithelial ovarian carcinoma subtypes. Our results showed distinct proteomic differences in CCOC compared with other epithelial ovarian cancer subtypes including alterations in lipid and purine metabolism pathways. Furthermore, we report potential clinically significant proteomic subgroups within CCOC, suggesting the biologic plausibility of stratified treatment for this cancer. Taken together, our results provide a comprehensive understanding of the CCOC proteomic landscape to facilitate future understanding and research of this disease. © 2022 The Pathological Society of Great Britain and Ireland.

In high‐grade ovarian carcinoma, platinum‐sensitive tumor recurrence and acquired‐resistance derive from quiescent residual cancer cells that overexpress CRYAB, CEACAM6, and SOX2

AbstractMost high‐grade ovarian carcinomas (HGOCs) are sensitive to carboplatin (CBP)‐based chemotherapy but frequently recur within 24 months. Recurrent tumors remain CBP‐sensitive and acquire resistance only after several treatment rounds. Recurrences arise from a small number of residual tumor cells not amenable to investigation in patients. We developed patient‐derived xenografts (PDXs) that allow the study of these different stages of CBP‐sensitive recurrence and acquisition of resistance. We generated PDX models from CBP‐sensitive and intrinsically resistant HGOC. PDXs were CBP‐ or mock‐treated and tumors were sampled, after treatment and at recurrence. We also isolated models with acquired‐resistance from CBP‐sensitive PDXs. Tumors were characterized at the histological and transcriptome levels. PDX models reproduced treatment response seen in the patients. CBP‐sensitive residual tumors contained nonproliferating tumor cell clusters embedded in a fibrotic mesh. In nontreated PDX tumors and treated CBP‐resistant tumors, fibrotic tissue was not prevalent. Residual tumors had marked differences in gene expression when compared to naïve and recurrent tumors, indicating downregulation of the cell cycle and proliferation and upregulation of interferon response and the epithelial–mesenchymal transition. This gene expression pattern resembled that described in embryonal diapause and ‘drug‐tolerant persister’ states. Residual and acquired‐resistance tumors share the overexpression of three genes: CEACAM6, CRYAB, and SOX2. Immunostaining analysis showed strong CEACAM6, CRYAB, and SOX2 protein expression in CBP‐sensitive residual and acquired‐resistance PDX, thus confirming the RNA profiling results. In HGOC PDX, CBP‐sensitive recurrences arise from a small population of quiescent, drug‐tolerant, residual cells embedded in a fibrotic mesh. These cells overexpress CEACAM6, CRYAB, and SOX2, whose overexpression is also associated with acquired resistance and poor patient prognosis. CEACAM6, CRYAB, and SOX2 may thus serve as a biomarker to predict recurrence and emergence of resistant disease in CBP‐treated HGOC patients. © 2022 The Pathological Society of Great Britain and Ireland.

Estradiol promotes cell survival and induces Greb1 expression in granulosa cell tumors of the ovary through an ERα‐dependent mechanism

AbstractGranulosa cell tumor (GCT) is a form of ovarian tumor characterized by its tendency to recur years after surgical ablation. Little is known about the mechanisms involved in GCT development and progression. GCTs can produce estradiol (E2), but whether this hormone could play a role in this cancer through its nuclear receptors, i.e. ERα and ERβ, remains unknown. Here, we addressed this issue by cell‐based and molecular studies on human GCTs and GCT cell lines. Importantly, we observed that E2 significantly increased the growth of GCT cells by promoting cell survival. The use of selective agonists of each type of receptor, together with Esr1 (ERα) or Esr2 (ERβ)‐deleted GCT cells, revealed that E2 mediated its effects through ERα‐dependent genomic mechanisms and ERβ/ERα‐dependent extra‐nuclear mechanisms. Notably, the expression of Greb1, a prototypical ER target gene, was dose‐dependently upregulated by E2 specifically through ERα in GCT cells. Accordingly, using GCTs from patients, we found that GREB1 mRNA abundance was positively correlated to intra‐tumoral E2 concentrations. Tissue microarray analyses showed that there were various combinations of ER expression in primary and recurrent GCTs, and that ERα expression persisted only in combination with ERβ in ~40% of recurrent tumors. Altogether, this study demonstrates that E2 can promote the progression of GCTs, with a clear dependence on ERα. In addition to demonstrating that GCTs can be classified as a hormone‐related cancer, our results also highlight that the nature of ER forms present in recurrent GCTs could underlie the variable efficiency of endocrine therapies. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Validated biomarker assays confirm that ARID1A loss is confounded with MMR deficiency, CD8 + TIL infiltration, and provides no independent prognostic value in endometriosis‐associated ovarian carcinomas

Abstract ARID1A (BAF250a) is a component of the SWI/SNF chromatin modifying complex, plays an important tumour suppressor role, and is considered prognostic in several malignancies. However, in ovarian carcinomas there are contradictory reports on its relationship to outcome, immune response, and correlation with clinicopathological features. We assembled a series of 1623 endometriosis‐associated ovarian carcinomas, including 1078 endometrioid (ENOC) and 545 clear cell (CCOC) ovarian carcinomas, through combining resources of the Ovarian Tumor Tissue Analysis (OTTA) Consortium, the Canadian Ovarian Unified Experimental Resource (COEUR), local, and collaborative networks. Validated immunohistochemical surrogate assays for ARID1A mutations were applied to all samples. We investigated associations between ARID1A loss/mutation, clinical features, outcome, CD8 + tumour‐infiltrating lymphocytes (CD8 + TILs), and DNA mismatch repair deficiency (MMRd). ARID1A loss was observed in 42% of CCOCs and 25% of ENOCs. We found no associations between ARID1A loss and outcomes, stage, age, or CD8 + TIL status in CCOC. Similarly, we found no association with outcome or stage in endometrioid cases. In ENOC, ARID1A loss was more prevalent in younger patients ( p  = 0.012) and was associated with MMRd ( p  < 0.001) and the presence of CD8 + TILs ( p  = 0.008). Consistent with MMRd being causative of ARID1A mutations, in a subset of ENOCs we also observed an association with ARID1A loss‐of‐function mutation as a result of small indels ( p  = 0.035, versus single nucleotide variants). In ENOC, the association with ARID1A loss, CD8 + TILs, and age appears confounded by MMRd status. Although this observation does not explicitly rule out a role for ARID1A influence on CD8 + TIL infiltration in ENOC, given current knowledge regarding MMRd, it seems more likely that effects are dominated by the hypermutation phenotype. This large dataset with consistently applied biomarker assessment now provides a benchmark for the prevalence of ARID1A loss‐of‐function mutations in endometriosis‐associated ovarian cancers and brings clarity to the prognostic significance. © 2021 The Pathological Society of Great Britain and Ireland.

Mechanisms of carboplatin‐ and paclitaxel‐dependent induction of premature senescence and pro‐cancerogenic conversion of normal peritoneal mesothelium and fibroblasts

Abstract Carboplatin (CPT) and paclitaxel (PCT) are the optimal non‐surgical treatment of epithelial ovarian cancer (EOC). Although their growth‐restricting influence on EOC cells is well known, their impact on normal peritoneal cells, including mesothelium (PMCs) and fibroblasts (PFBs), is poorly understood. Here, we investigated whether, and if so, by what mechanism, CPT and PCT induce senescence of omental PMCs and PFBs. In addition, we tested whether PMC and PFB exposure to the drugs promotes the development of a pro‐cancerogenic phenotype. The results showed that CPT and PCT induce G2/M growth arrest‐associated senescence of normal peritoneal cells and that the strongest induction occurs when the drugs act together. PMCs senesce telomere‐independently with an elevated p16 level and via activation of AKT and STAT3. In PFBs, telomeres shorten along with an induction of p21 and p53, and their senescence proceeds via the activation of ERK1/2. Oxidative stress in CPT + PCT‐treated PMCs and PFBs is extensive and contributes causatively to their premature senescence. Both PMCs and PFBs exposed to CPT + PCT fuel the proliferation, migration, and invasion of established (A2780, OVCAR‐3, SKOV‐3) and primary EOCs, and this activity is linked with an overproduction of multiple cytokines altering the cancer cell transcriptome and controlled by p38 MAPK, NF‐κB, STAT3, Notch1, and JAK1. Collectively, our findings indicate that CPT and PCT lead to iatrogenic senescence of normal peritoneal cells, which paradoxically and opposing therapeutic needs alters their phenotype towards pro‐cancerogenic. It cannot be excluded that these adverse outcomes of chemotherapy may contribute to EOC relapse in the case of incomplete tumor eradication and residual disease initiation. © 2023 The Pathological Society of Great Britain and Ireland.

ERBB2 amplification is a late event in the pathogenesis of high‐grade endometrial carcinomas with heterogeneous HER2 expression

Abstract Intratumor heterogeneity of ERBB2 amplification/HER2 overexpression is frequently observed in ERBB2 ‐amplified high‐grade endometrial carcinoma (HG‐EC) and contributes to anti‐HER2 therapy resistance. To elucidate the molecular pathogenesis and evolutionary trajectory of HER2‐heterogeneous HG‐ECs, we performed next‐generation sequencing of spatially distinct HER2‐negative (HER2−) and HER2‐positive (HER2+) tumor areas from nine tumors (whole exome, n  = 7; targeted panel, n  = 2). HER2− and HER2+ components shared a high proportion of somatic mutations, particularly clonal mutations, including known EC driver genetic alterations. The 17q12 amplicon, containing the ERBB2 gene, was the only significant recurrent copy number alteration that differed between HER2− and HER2+ components. By unsupervised hierarchical clustering of genome‐wide copy number alterations, samples clustered together at the patient level rather than by HER2 status. Intra‐ and intertumor heterogeneity in ERBB2 amplification/HER2 expression was also observed in metastatic lesions, which likely originated from different tumor subpopulations within the primary tumor. Exploratory spatial transcriptomics analyses revealed gene expression differences associated with HER2 status, including a shift from ‘mesenchymal‐like’ toward epithelial differentiation in HER2+ components for a subset of cases, a finding that warrants further investigation. Our results suggest that HER2 heterogeneity in HG‐EC reflects late acquisition of ERBB2 amplification during tumor evolution. ERBB2 does not appear to drive tumor initiation in HER2‐heterogeneous HG‐EC but likely serves a context‐dependent role in the progression of established tumors. © 2026 The Pathological Society of Great Britain and Ireland.

Cell state dynamics during early stages of serous endometrial carcinoma

AbstractSerous endometrial carcinoma (SEC) is one of the most lethal types of uterine cancer, responsible for about 40% of all endometrial cancer‐related deaths. Cell state dynamics during the early stages of SEC remain largely unknown, thereby hindering early detection and treatment of this disease. Here, we provide a comprehensive census of cell types and their states for normal, predysplastic, and dysplastic endometrium in a genetic mouse model of SEC. We report that predysplastic changes are characterized by increasingly diverse immature luminal epithelial cell populations. The decrease in differentiated cell states is accompanied by the emergence of a ‘single‐cell and spatial transcriptome dysregulation’ gene signature. This signature contains seven genes that predict poor patient prognosis and are promising diagnostic markers and therapeutic targets. In summary, our results suggest an important role of the luminal epithelial cell state in SEC pathogenesis and validate our mouse SEC model as a capable comparative platform for preclinical studies. © 2025 The Pathological Society of Great Britain and Ireland.

High‐grade endometrial stromal sarcoma is closely related to BCOR ‐altered sarcomas of the soft tissue and kidney rather than to other uterine sarcomas: implications for uterine sarcoma classification

Abstract High‐grade endometrial stromal sarcoma (HGESS), which was not recognized as a distinct entity in the third edition of the World Health Organization (WHO) classification and was therefore included in the undifferentiated uterine sarcoma (UUS) category, was reestablished as a separate entity in the fourth edition. HGESS shares BCL‐6 corepressor (BCOR) alterations with undifferentiated small round‐cell sarcoma (USRCS) of the soft tissue and clear cell sarcoma of the kidney (CCSK). This study aims to perform a comparative morphological, immunohistochemical, and molecular analysis of HGESS, UUS, USRCS, and CCSK. Consecutive uterine sarcomas diagnosed as HGESS or UUS were reviewed and compared to BCOR ‐ altered USRCS ( n  = 28) and CCSK ( n  = 10) (including both previously published and new cases). Molecular, DNA methylome (DNAm), and copy number variation (CNV) analyses were performed. DNAm data of 93 previously analyzed uterine and round‐cell tumors of several different types were used for clustering analysis. Twenty‐five uterine sarcomas (six HGESS and 19 UUS) were included; five of six HGESS cases showed fusions associated with BCOR alterations ( YWHAE :: NUTM2A/B, EPC1 :: KDM2B, ZC3H7B :: BCOR ); UUS showed no fusions ( n  = 15) or fusions unrelated to BCOR alterations ( n  = 4). All USRCS and CCSK cases showed either BCOR‐ITD or BCOR alteration‐related fusions. BCOR‐altered HGESS showed broad morphological and immunophenotypic overlap with USRCS and CCSK. DNAm analysis showed that BCOR ‐altered HGESS, USRCS, and CCSK clustered together, separately from all other tumor types. The non‐BCOR‐altered HGESS showed a JAZF1 :: SUZ12 fusion and arose from a low‐grade endometrial stromal sarcoma component. CNVs were found in 15/16 uterine sarcomas and in 16/36 USRCS/CCSK cases. BCOR‐altered HGESS appeared to be closely related to BCOR‐altered USRCS and CCSK rather than to other uterine sarcomas. We suggest that HGESS with BCOR alterations may warrant reclassification as ‘BCOR‐altered uterine sarcomas’. © 2026 The Pathological Society of Great Britain and Ireland.

Decreased HER2 expression in endometrial cancer following anti‐HER2 therapy

Abstract Trastuzumab has demonstrated clinical efficacy in the treatment of HER2‐positive serous endometrial cancer (EC), which led to its incorporation into standard‐of‐care management of this aggressive disease. Acquired resistance remains an important challenge, however, and its underlying mechanisms in EC are unknown. To define the molecular changes that occur in response to anti‐HER2 therapy in EC, targeted next‐generation sequencing (NGS), HER2 immunohistochemistry (IHC), and fluorescence in situ hybridization (FISH) were performed on pre‐ and post‐treatment tumour samples from 14 patients with EC treated with trastuzumab or trastuzumab emtansine. Recurrent tumours after anti‐HER2 therapy acquired additional genetic alterations compared with matched pre‐treatment ECs and frequently showed decreased HER2 protein expression by IHC (7/14, 50%). Complete/near‐complete absence of HER2 protein expression (score 0/1+) observed post‐treatment (4/14, 29%) was associated with retained HER2 gene amplification ( n  = 3) or copy number neutral status ( n  = 1). Whole‐exome sequencing performed on primary and recurrent tumours from the latter case, which exhibited genetic heterogeneity of HER2 amplification in the primary tumour, revealed selection of an early HER2 ‐non‐amplified clone following therapy. Our findings demonstrate that loss of target expression, by selection of HER2 ‐non‐amplified clones or, more commonly, by downregulation of expression, may constitute a mechanism of resistance to anti‐HER2 therapy in HER2‐positive EC. © 2023 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Endometrial carcinoma: molecular subtypes, precursors and the role of pathology in early diagnosis

AbstractEndometrial carcinoma (EC) is classified into a wide range of morphological variants; this list has expanded over the past decade with the inclusion of mesonephric‐like and dedifferentiated carcinoma as EC variants in the fifth edition of the WHO Classification of Female Genital Tumours, and recognition that carcinosarcoma is a biphasic carcinoma rather than a sarcoma. Each EC variant has distinct molecular abnormalities, including TCGA‐based molecular subtypes, allowing further subclassification and adding complexity. In contrast to this rapid progress in understanding EC, there are only two recognized EC precursor lesions: endometrial atypical hyperplasia/endometrioid intraepithelial neoplasia (EAH/EIN) and serous intraepithelial carcinoma, a situation that has not changed for many years. Diagnosis of EC precursors is a cornerstone of surgical pathology practice, with early diagnosis contributing to the relatively favorable prognosis of EC. In this review we relate the precursor lesions to each of the EC morphological variants and molecular subtypes, discuss how successful early diagnosis is for each variant/molecular subtype and how it might be improved, and identify knowledge gaps where there is insufficient understanding of EC histogenesis. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Adiponectin deficiency promotes endometrial carcinoma pathogenesis and development via activation of mitogen‐activated protein kinase

AbstractObesity is one of the major risk factors for cancer. Clinical studies have demonstrated that circulating levels of adiponectin are inversely correlated, not only with the extent of adiposity, but also with the incidence of several types of cancer, particularly endometrial cancer (EC). However, thus far, adiponectin remains a correlative factor, without definitive evidence to show a causal effect in EC and the potential mechanism(s) involved. To address this issue, we introduced an Apn‐null mutation into Pten haploid‐deficient (Pten+/−) mice. The Pten heterozygous mutation alone led to the development of EC in less than 30% of female mice; however, when combined with the Apn‐null mutation, the incidence of endometrial lesions rose to at least two‐thirds. Although Apn deficiency did not further potentiate the Akt activation caused by the Pten mutation, it elevated the phosphorylation of mitogen‐activated protein kinase (MAPK) p42/44, indicating activation of the MAPK signaling pathway. Treatment of Apn−/−;Pten+/− mice with a MEK inhibitor blocked the development of EC. Finally, xenografts of a PTEN‐proficient human EC cell line grew faster in Apn‐deficient mice, whereas an adiponectin receptor agonist reduced xenograft growth of a PTEN‐deficient human EC cell line. Thus, reduction of adiponectin activity promotes EC development, at least in the context of Pten mutation, by activating MAPK. © 2022 The Pathological Society of Great Britain and Ireland.

Computational augmentation of neoplastic endometrial glands in digital pathology displays

AbstractThe pathologic diagnosis of neoplasia requires localization and classification of lesional tissue, a process that depends on the recognition of an abnormal spatial distribution of neoplastic elements relative to admixed normal background tissue. In endometrial intraepithelial neoplasia (EIN), a pre‐cancer usually managed by hysterectomy, a clonally mutated proliferation of cytologically altered glands (‘neoplastic‐EIN’) aggregates in clusters that also contain background non‐neoplastic glands (‘background‐NL’). Here, we used image analysis to classify individual glands within endometrial tissue fragments as neoplastic‐EIN or background‐NL, and we used the distribution of predictions to localize foci diagnostic of EIN. Nuclear coordinates were automatically assigned and were used as vertices to generate Delaunay triangulations for each gland. Graph statistical variables were used to develop random forest algorithms to classify glands as neoplastic‐EIN or background‐NL. Individual glands in an independent validation set were scored by a ‘ground truth’ biomarker (PAX2 immunohistochemistry). We found that exclusion of small glands led to improvement in classification accuracy. Using an inclusion threshold of 200 nuclei per gland, our final model classification accuracy was 77.5% in the validation set, with a positive predictive value of 0.81. We leveraged this high positive predictive value in a point cloud overlay display to assist end‐user identification of EIN foci. This study demonstrates that graph theory approaches applied to small‐scale anatomic elements in the endometrium allow biologic classification by machine learning, and that spatial superimposition over large‐scale tissue expanses can have practical diagnostic utility. We expect this augmented diagnostic approach to be generalizable to commonly encountered problems in other organ systems. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Genome‐wide mutation analysis in precancerous lesions of endometrial carcinoma

Abstract Clinicopathological evidence supports endometrial atypical hyperplasia (AH) or endometrial intraepithelial neoplasia as the precursor of uterine endometrioid carcinoma (EC), the most common gynecologic malignancy. However, the pathogenic progression from AH to EC remains unclear. Here, we employed whole‐exome sequencing to identify somatic mutations and copy number changes in micro‐dissected lesions from 30 pairs of newly diagnosed AH and EC. We found that all but one pair of AHs shared the same DNA mismatch repair status as their corresponding ECs. The percentage of common mutations between AH lesions and corresponding ECs varied significantly, ranging from 0.1% to 82%. Microsatellite stable AHs had fewer cancer driver mutations than ECs (5 versus 7, p  = 0.017), but among microsatellite unstable AHs and ECs there was no difference in mutational numbers (36 versus 38, p  = 0.65). As compared to AH specimens, 19 (79%) of 24 microsatellite stable EC tumors gained new cancer driver mutations, most of which involved PTEN , ARID1A , PIK3CA , CTNNB1 , or CHD4 . Our results suggest that some AH lesions are the immediate precursor of ECs, and progression depends on acquisition of additional cancer driver mutations. However, a complex clonal relationship between AH and EC can also be appreciated, as in some cases both lesions diverge very early or arise independently, thus co‐developing with distinct genetic trajectories. Our genome‐wide profile of mutations in AH and EC shines new light on the molecular landscape of tumor progression. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Single cell transcriptomes of normal endometrial derived organoids uncover novel cell type markers and cryptic differentiation of primary tumours

AbstractEndometrial carcinoma, the most common gynaecological cancer, develops from endometrial epithelium which is composed of secretory and ciliated cells. Pathologic classification is unreliable and there is a need for prognostic tools. We used single cell sequencing to study organoid model systems derived from normal endometrial endometrium to discover novel markers specific for endometrial ciliated or secretory cells. A marker of secretory cells (MPST) and several markers of ciliated cells (FAM92B, WDR16, and DYDC2) were validated by immunohistochemistry on organoids and tissue sections. We performed single cell sequencing on endometrial and ovarian tumours and found both secretory‐like and ciliated‐like tumour cells. We found that ciliated cell markers (DYDC2, CTH, FOXJ1, and p73) and the secretory cell marker MPST were expressed in endometrial tumours and positively correlated with disease‐specific and overall survival of endometrial cancer patients. These findings suggest that expression of differentiation markers in tumours correlates with less aggressive disease, as would be expected for tumours that retain differentiation capacity, albeit cryptic in the case of ciliated cells. These markers could be used to improve the risk stratification of endometrial cancer patients, thereby improving their management. We further assessed whether consideration of MPST expression could refine the ProMiSE molecular classification system for endometrial tumours. We found that higher expression levels of MPST could be used to refine stratification of three of the four ProMiSE molecular subgroups, and that any level of MPST expression was able to significantly refine risk stratification of the copy number high subgroup which has the worst prognosis. Taken together, this shows that single cell sequencing of putative cells of origin has the potential to uncover novel biomarkers that could be used to guide management of cancers. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Molecular pathology of Lynch syndrome

AbstractLynch syndrome (LS) is characterised by predisposition to colorectal, endometrial, and other cancers and is caused by inherited pathogenic variants affecting the DNA mismatch repair (MMR) genes MLH1, MSH2, MSH6, and PMS2. It is probably the most common predisposition to cancer, having an estimated prevalence of between 1/100 and 1/180. Resources such as the International Society for Gastrointestinal Hereditary Cancer's MMR gene variant database, the Prospective Lynch Syndrome Database (PLSD), and the Colon Cancer Family Register (CCFR), as well as pathological and immunological studies, are enabling advances in the understanding of LS. These include defined criteria by which to interpret gene variants, the function of MMR in the normal control of apoptosis, definition of the risks of the various cancers, and the mechanisms and pathways by which the colorectal and endometrial tumours develop, including the critical role of the immune system. Colorectal cancers in LS can develop along three pathways, including flat intramucosal lesions, which depend on the underlying affected MMR gene. This gives insights into the limitations of colonoscopic surveillance and highlights the need for other forms of anti‐cancer prophylaxis in LS. Finally, it shows that the processes of autoimmunisation and immunoediting fundamentally constrain the development of tumours in LS and explain the efficacy of immune checkpoint blockade therapy in MMR‐deficient tumours. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

p53 immunohistochemistry is an accurate surrogate for TP53 mutational analysis in endometrial carcinoma biopsies

AbstractTP53 mutations are considered a surrogate biomarker of the serous‐like ‘copy number high’ molecular subtype of endometrial carcinoma (EC). In ovarian carcinoma, p53 immunohistochemistry (IHC) accurately reflects mutational status with almost 100% specificity but its performance in EC has not been established. This study tested whether p53 IHC reliably predicts TP53 mutations identified by next‐generation sequencing (NGS) in EC biopsy samples for all ECs and as part of a molecular classification algorithm after exclusion of cases harbouring mismatch repair defects (MMRd) or pathogenic DNA polymerase epsilon exonuclease domain mutations (POLEmut). A secondary aim assessed inter‐laboratory variability in p53 IHC. From a total of 207 cases from five centres (37–49 cases per centre), p53 IHC carried out at a central reference laboratory was compared with local IHC (n = 164) and curated tagged‐amplicon NGS TP53 sequencing results (n = 177). Following consensus review, local and central p53 IHC results were concordant in 156/164 (95.1%) tumours. Discordant results were attributable to both interpretive and technical differences in staining between the local and central laboratories. When results were considered as any mutant pattern versus wild‐type pattern staining, however, there was disagreement between local and central review in only one case. The concordance between p53 IHC and TP53 mutation was 155/168 (92.3%) overall, and 117/123 (95.1%) after excluding MMRd and POLEmut EC. Three (3/6) discordant results were in serous carcinomas with complete absence of p53 staining but no detectable TP53 mutation. Subclonal mutant p53 IHC expression was observed in 9/177 (5.1%) cases, of which four were either MMRd or POLEmut. Mutant pattern p53 IHC was observed in 63/63 (100%) serous carcinomas that were MMR‐proficient/POLE exonuclease domain wild‐type. Optimised p53 IHC performs well as a surrogate test for TP53 mutation in EC biopsies, demonstrates excellent inter‐laboratory reproducibility, and has high clinical utility for molecular classification algorithms in EC. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Genomic catastrophe, the peritoneal cavity and ovarian cancer prevention

AbstractThe current theory of carcinogenesis for the deadliest of ‘ovarian’ cancers—high‐grade serous carcinoma (HGSC)—holds that the malignancy develops first in the fallopian tube and spreads to the ovaries, peritoneum, and/or regional lymph nodes. This is based primarily on the observation of early forms of serous neoplasia (serous tubal intraepithelial lesions [STILs], and serous tubal intraepithelial carcinomas [STICS]) in the fimbria of women undergoing risk reduction surgery. However, these lesions are uncommon in the general population, confer a low risk (5%) of HGSC following their removal in at‐risk women with germ‐line BRCA1/2 mutations, and require 4 or more years to recur as intraperitoneal HGSC. These features suggest that isolated STILs and STICs behave as precursors, with uncertain cancer risk rather than carcinomas. Their evolution to HGSC within, or after, escape from the tube could proceed stepwise with multiple biologic events; however, it is unclear whether tubal or ovarian HGSCs encountered in the setting of advanced disease evolved in the same fashion. The latter scenario could also be explained by a ‘catastrophic’ model in which STICs suddenly develop with invasive and metastatic potential, overwhelming or obscuring the site of origin. Moreover, a similar model might explain the sudden emergence of HGSC in the peritoneal cavity following escape of precursor cells years before. Long‐term follow‐up data from opportunistic or prophylactic salpingectomy should shed light on where malignant transformation occurs, as well as the timeline from precursor to metastatic HGSC. © 2022 The Pathological Society of Great Britain and Ireland.

Integrated morphological, immunohistochemical, and genomic profiling identifies uterine leiomyoma patients with hereditary leiomyomatosis and renal cell cancer syndrome: a comprehensive analysis of 252 cases

Abstract Fumarate hydratase‐deficient uterine leiomyomas (FHd‐ULMs) represent a molecularly distinct subgroup of smooth muscle tumours associated with hereditary leiomyomatosis and renal cell cancer (HLRCC) syndrome. This study determined the detection rate of germline pathogenic FH variants in FHd‐ULMs using paired tumour‐normal sequencing and assessed the utility of integrated morphological, immunohistochemical (FH/2SC), genomic, and clinical features for selecting cases suspected of HLRCC. Histopathological assessment of the 252 FHd‐ULMs revealed consistent morphological features, whereas molecular profiling identified three biologically distinct categories. Germline FH ‐mutated (hereditary) cases constituted 35.7% (74/207) of this FHd‐ULM cohort, four of which showed concomitant somatic copy‐number alterations. This contrasted with the somatic‐mutated subgroup, which comprised 50.7% (105/207), including 18.4% (38/207) with isolated somatic copy‐number losses. The remaining 13.6% (28/207), though lacking detectable FH mutations, were classified with somatic‐mutated cases as sporadic FHd‐ULMs based on shared clinicopathological features. Molecular analysis identified shared variant distributions across exons 2–10, with exons 5 and 7 in the fumarate lyase domain emerging as the predominant mutational hotspots. Notably, truncating mutations showed significantly higher prevalence in hereditary cases versus somatic variants ( p  < 0.01). Clinically, hereditary FHd‐ULMs presented at younger ages (< 45 years) and manifested more aggressive phenotypes, including elevated rates of infertility (54.1% versus 26.4%), multifocal tumour development (86.5% versus 53.4%), increased surgical interventions (44.6% versus 11.5%), and familial leiomyoma clustering (51.4% versus 24.2%). Our results identify germline FH mutations, which confer significant HLRCC risk, in 35.7% of FHd‐ULMs, while somatic alterations account for the majority of cases. To ensure efficient resource allocation, we propose a stratified diagnostic approach: initial universal FH/2SC immunohistochemical screening for ULMs displaying ≥ 3 FH‐deficient morphological features, followed by confirmatory genetic testing in high‐risk individuals, defined by either aberrant FH/2SC immunoreactivity or, in immunohistochemically normal cases, age < 45 years together with a personal/family history of multiple symptomatic leiomyomas or HLRCC‐associated neoplasms. © 2026 The Pathological Society of Great Britain and Ireland.

From morphology to methylome: epigenetic studies of Müllerian mesonephric‐like adenocarcinoma reveal similarities to cervical mesonephric adenocarcinoma†

AbstractMesonephric adenocarcinomas (MAs) and mesonephric‐like adenocarcinomas (MLAs) are rare, aggressive neoplasms that arise in the gynecologic tract and show overlapping morphologic, immunohistochemical, and molecular features. While MAs occur in the cervix and are thought to arise from mesonephric remnants, MLAs occur in the endometrium and ovary and are believed to originate from transdifferentiation of Müllerian lesions. Both MAs and MLAs show a variety of architectural patterns, exhibit frequent expression of GATA3 by immunohistochemistry, and harbor KRAS mutations. In a recent article published in The Journal of Pathology, Kommoss and colleagues used DNA methylation profiling to extend these similarities and showed that MLAs and MAs cluster together based on their epigenetic signatures and are epigenetically distinct from other Müllerian adenocarcinomas. They also showed that MLAs and MAs harbor a high number of global copy number alterations. This study provides evidence that MLAs more closely resemble MAs than Müllerian carcinomas on an epigenetic level. As a result, the authors argue that MLA should be renamed ‘mesonephric‐type adenocarcinoma.’ Further research is needed to establish the relationship between these two entities, their etiology, and pathogenesis. © 2024 The Pathological Society of Great Britain and Ireland.

Small cell neuroendocrine carcinoma of the cervix: diagnostic challenges and emerging molecular insights †

Abstract Small cell neuroendocrine carcinoma of the cervix (SCNECC) is a rare and highly aggressive malignancy with poor prognosis that predominantly affects premenopausal women. Histopathological evaluation is central to diagnosis and clinical management; however, distinguishing SCNECC from other ‘small blue round cell’ malignancies often requires a multimodal approach that integrates morphology, immunohistochemistry, and advanced molecular testing. In the absence of specific and sensitive biomarkers, SCNECC largely remains a diagnosis of exclusion, underscoring the need for comprehensive diagnostic algorithms. A study by Pan, Yan, Yuan et al employed whole transcriptome profiling and identified three molecular subgroups within SCNECC. Importantly, one subgroup displayed an inflamed phenotype, characterized by high expression of MHC‐II complex and IFN‐α/β–related genes, suggesting potential susceptibility to immunotherapy, a finding that mirrors observations in small cell lung cancer. These findings highlight the biological heterogeneity of SCNECC and reinforce the importance of integrating molecular data to refine diagnostic accuracy and guide therapeutic decision‐making. This commentary emphasizes the pressing need for comprehensive diagnostics and further research to advance treatment strategies for this rare and challenging malignancy. © 2025 The Pathological Society of Great Britain and Ireland.

Cytoplasmic SIRT1 promotes paclitaxel resistance in ovarian carcinoma through increased formation and survival of polyploid giant cancer cells

AbstractTherapeutic resistance is a notable cause of death in patients with ovarian carcinoma. Polyploid giant cancer cells (PGCCs), commonly arising in tumor tissues following chemotherapy, have recently been considered to contribute to drug resistance. As a type III deacetylase, Sirtuin1 (SIRT1) plays essential roles in the cell cycle, cellular senescence, and drug resistance. Accumulating evidence has suggested that alteration in its subcellular localization via nucleocytoplasmic shuttling is a critical process influencing the functions of SIRT1. However, the roles of SIRT1 subcellular localization in PGCC formation and subsequent senescence escape remain unclear. In this study, we compared the differences in the polyploid cell population and senescence state of PGCCs following paclitaxel treatment between tumor cells overexpressing wild‐type SIRT1 (WT SIRT1) and those expressing nuclear localization sequence (NLS)‐mutated SIRT1 (SIRT1NLSmt). We investigated the involvement of cytoplasmic SIRT1 in biological processes and signaling pathways, including the cell cycle and cellular senescence, in ovarian carcinoma cells' response to paclitaxel treatment. We found that the SIRT1NLSmt tumor cell population contained more polyploid cells and fewer senescent PGCCs than the SIRT1‐overexpressing tumor cell population. Comparative proteomic analyses using co‐immunoprecipitation (Co‐IP) combined with liquid chromatography–mass spectrometry (LC‐MS)/MS showed the differences in the differentially expressed proteins related to PGCC formation, cell growth, and death, including CDK1 and CDK2, between SIRT1NLSmt and SIRT1 cells or PGCCs. Our results suggested that ovarian carcinoma cells utilize polyploidy formation as a survival mechanism during exposure to paclitaxel‐based treatment via the effect of cytoplasmic SIRT1 on PGCC formation and survival, thereby boosting paclitaxel resistance. © 2023 The Pathological Society of Great Britain and Ireland.

Multiomics sequencing and immune microenvironment characteristics define three subtypes of small cell neuroendocrine carcinoma of the cervix

AbstractSmall cell cervical carcinoma (SCCC) is the most common neuroendocrine tumor in the female genital tract, with an unfavorable prognosis and lacking an evidence‐based therapeutic approach. Until now, the distinct subtypes and immune characteristics of SCCC combined with genome and transcriptome have not been described. We performed genomic (n = 18), HPV integration (n = 18), and transcriptomic sequencing (n = 19) of SCCC samples. We assessed differences in immune characteristics between SCCC and conventional cervical cancer, and other small cell neuroendocrine carcinomas, through bioinformatics analysis and immunohistochemical assays. We stratified SCCC patients through non‐negative matrix factorization and described the characteristics of these distinct types. We further validated it using multiplex immunofluorescence (n = 77) and investigated its clinical prognostic effect. We confirmed a high frequency of PIK3CA and TP53 alterations and HPV18 integrations in SCCC. SCCC and other small cell carcinoma had similar expression signatures and immune cell infiltration patterns. Comparing patients with SCCC to those with conventional cervical cancer, the former presented immune excluded or ‘desert’ infiltration. The number of CD8+ cells in the invasion margin of SCCC patients predicted favorable clinical outcomes. We identified three transcriptome subtypes: an inflamed phenotype with high‐level expression of genes related to the MHC‐II complex (CD74) and IFN‐α/β (SCCC‐I), and two neuroendocrine subtypes with high‐level expression of ASCL1 or NEUROD1, respectively. Combined with multiple technologies, we found that the neuroendocrine groups had more TP53 mutations and SCCC‐I had more PIK3CA mutations. Multiplex immunofluorescence validated these subtypes and SCCC‐I was an independent prognostic factor of overall survival. These results provide insights into SCCC tumor heterogeneity and potential therapies. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Targeting carcinoma‐associated mesothelial cells with antibody–drug conjugates in ovarian carcinomatosis

AbstractOvarian carcinomatosis is characterized by the accumulation of carcinoma‐associated mesothelial cells (CAMs) in the peritoneal stroma and mainly originates through a mesothelial‐to‐mesenchymal transition (MMT) process. MMT has been proposed as a therapeutic target for peritoneal metastasis. Most ovarian cancer (OC) patients present at diagnosis with peritoneal seeding, which makes tumor progression control difficult by MMT modulation. An alternative approach is to use antibody–drug conjugates (ADCs) targeted directly to attack CAMs. This strategy could represent the cornerstone of precision‐based medicine for peritoneal carcinomatosis. Here, we performed complete transcriptome analyses of ascitic fluid‐isolated CAMs in advanced OC patients with primary‐, high‐, and low‐grade, serous subtypes and following neoadjuvant chemotherapy. Our findings suggest that both cancer biological aggressiveness and chemotherapy‐induced tumor mass reduction reflect the MMT‐associated changes that take place in the tumor surrounding microenvironment. Accordingly, MMT‐related genes, including fibroblast activation protein (FAP), mannose receptor C type 2 (MRC2), interleukin‐11 receptor alpha (IL11RA), myristoylated alanine‐rich C‐kinase substrate (MARCKS), and sulfatase‐1 (SULF1), were identified as specific actionable targets in CAMs of OC patients, which is a crucial step in the de novo design of ADCs. These cell surface target receptors were also validated in peritoneal CAMs of colorectal cancer peritoneal implants, indicating that ADC‐based treatment could extend to other abdominal tumors that show peritoneal colonization. As proof of concept, a FAP‐targeted ADC reduced tumor growth in an OC xenograft mouse model with peritoneal metastasis‐associated fibroblasts. In summary, we propose MMT as a potential source of ADC‐based therapeutic targets for peritoneal carcinomatosis. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Cystathionine gamma‐lyase‐mediated hypoxia inducible factor 1‐alpha expression drives clear cell ovarian cancer progression

AbstractClear cell ovarian cancer (CCOC) is the second most common ovarian cancer subtype, accounting for 5%–11% of ovarian cancers in North America. Late‐stage CCOC is associated with a worse prognosis compared to other ovarian cancer histotypes, a challenge that has seen limited progress in recent decades. CCOC typically originates within the toxic microenvironment of endometriotic ovarian cysts and is characterized by its intrinsic chemoresistance, a strong hypoxic signature, and abundant expression of cystathionine gamma‐lyase (CTH). CTH is a key enzyme in the transsulfuration pathway and serves as a marker of ciliated cells derived from the Müllerian tract. CTH plays a pivotal role in de novo cysteine synthesis, which is essential for glutathione (GSH) production and redox homeostasis. Using an array of molecular tools and cancer models, including in vivo studies, we demonstrated that CTH expression was induced under various stress conditions, such as exposure to endometriotic cyst content and hypoxia. This induction enables cell survival and creates a differentiation state manifested by CCOC that potentiates tumor progression and metastasis. In addition to regulating redox homeostasis, CTH enhances hypoxia inducible factor 1‐alpha (HIF1α) expression, independently of hydrogen sulfide (H2S) production. Re‐expression of HIF1α in CTH KO cells fully restored metastatic capacity in in vivo models. Co‐expression of CTH and HIF1α proteins was also observed in human CCOC samples. Importantly, targeting CTH in CCOC significantly reduced its metastatic potential in in vivo models and enhanced sensitivity to chemotherapy. These findings underscore that CTH is both a defining feature of CCOC and a promising therapeutic target, not only for CCOC patients but also for those with other CTH‐expressing cancers. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Ovarian high‐grade serous carcinoma cells with low SMARCA4 expression and high SMARCA2 expression contribute to platinum resistance

AbstractPlatinum resistance is a major obstacle to the treatment of ovarian cancer and is correlated with poor clinical outcomes. Intratumor heterogeneity plays a key role in chemoresistance. Recent studies have emphasized the contributions of genetic and epigenetic factors to the development of intratumor heterogeneity. Although the clinical significance of multi‐subunit chromatin remodeler, switch/sucrose nonfermenting (SWI/SNF) complexes in cancers has been reported, the impacts of SWI/SNF‐related, matrix‐associated, actin‐dependent regulator of chromatin, subfamily A, member 4/subfamily A, member 2 (SMARCA4/A2) expression patterns in human cancer tissues have not been fully elucidated. Here, we show that low expression of SMARCA4 and high expression of SMARCA2 are associated with platinum resistance in ovarian high‐grade serous carcinoma (HGSC) cells. We used fluorescence multiplex immunohistochemistry (fmIHC) to study resected specimens; we examined heterogeneity in human HGSC tissues at the single‐cell level, which revealed that the proportion of cells with the SMARCA4low/SMARCA2high phenotype was positively correlated with clinical platinum‐resistant recurrence. We used stable transfection of SMARCA2 and siRNA knockdown of SMARCA4 to generate HGSC cells with the SMARCA4low/SMARCA2high phenotype; these cells had the greatest resistance to carboplatin. Bioinformatics analyses revealed that the underlying mechanism involved in substantial alterations to chromatin accessibility and resultant fibroblast growth factor (FGF) signaling activation, MAPK pathway activation, BCL2 overexpression, and reduced carboplatin‐induced apoptosis; these were confirmed by in vitro functional experiments. Furthermore, in vivo experiments in an animal model demonstrated that combination therapy with carboplatin and a fibroblast growth factor receptor (FGFR) inhibitor promoted cell death in HGSC xenografts. Taken together, these observations reveal a specific subpopulation of HGSC cells that is associated with clinical chemoresistance, which may lead to the establishment of a histopathological prediction system for carboplatin response. Our findings may facilitate the development of novel therapeutic strategies for platinum‐resistant HGSC cells. © 2023 The Pathological Society of Great Britain and Ireland.

Genomic analysis of low‐grade serous ovarian carcinoma to identify key drivers and therapeutic vulnerabilities

Abstract Low‐grade serous ovarian carcinoma (LGSOC) is associated with a poor response to existing chemotherapy, highlighting the need to perform comprehensive genomic analysis and identify new therapeutic vulnerabilities. The data presented here represent the largest genetic study of LGSOCs to date ( n  = 71), analysing 127 candidate genes derived from whole exome sequencing cohorts to generate mutation and copy‐number variation data. Additionally, immunohistochemistry was performed on our LGSOC cohort assessing oestrogen receptor, progesterone receptor, TP53, and CDKN2A status. Targeted sequencing identified 47% of cases with mutations in key RAS/RAF pathway genes ( KRAS , BRAF , and NRAS ), as well as mutations in putative novel driver genes including USP9X (27%), MACF1 (11%), ARID1A (9%), NF2 (4%), DOT1L (6%), and ASH1L (4%). Immunohistochemistry evaluation revealed frequent oestrogen/progesterone receptor positivity (85%), along with CDKN2A protein loss (10%) and CDKN2A protein overexpression (6%), which were linked to shorter disease outcomes. Indeed, 90% of LGSOC samples harboured at least one potentially actionable alteration, which in 19/71 (27%) cases were predictive of clinical benefit from a standard treatment, either in another cancer's indication or in LGSOC specifically. In addition, we validated ubiquitin‐specific protease 9X (USP9X), which is a chromosome X‐linked substrate‐specific deubiquitinase and tumour suppressor, as a relevant therapeutic target for LGSOC. Our comprehensive genomic study highlighted that there is an addiction to a limited number of unique ‘driver’ aberrations that could be translated into improved therapeutic paths. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

A multi‐ethnic analysis of immune‐related gene expression signatures in patients with ovarian clear cell carcinoma

AbstractLittle is known about the immune environment of ovarian clear cell carcinoma (OCCC) and its impact on various ethnic backgrounds. The aim of this OCCC immune‐related gene expression signatures (irGES) study was to address the interaction between tumour and immune environment of ethnically‐diverse Asian and Caucasian populations and to identify relevant molecular subsets of biological and clinical importance. Our study included 264 women from three different countries (Singapore, Japan, and the UK) and identified four novel immune subtypes (PD1‐high, CTLA4‐high, antigen‐presentation, and pro‐angiogenic subtype) with differentially expressed pathways, and gene ontologies using the NanoString nCounter PanCancer Immune Profiling Panel. The PD1‐high and CTLA4‐high subtypes demonstrated significantly higher PD1, PDL1, and CTLA4 expression, and were associated with poorer clinical outcomes. Mismatch repair (MMR) protein expression, assessed by immunohistochemistry, revealed that about 5% of OCCCs had deficient MMR expression. The prevalence was similar across the three countries and appeared to cluster in the CTLA4‐high subtype. Our results suggest that OCCC from women of Asian and Caucasian descent shares significant clinical and molecular similarities. To our knowledge, our study is the first study to include both Asian and Caucasian women with OCCC and helps to shine light on the impact of ethnic differences on the immune microenvironment of OCCC. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Molecular genetic evidence supporting diverse histogenic origins of germ cell tumors

AbstractGerm cell tumors (GCTs) originate during the histogenesis of primordial germ cells to mature gametes. Previous studies identified five histogenic mechanisms in ovarian mature teratomas (type I: failure of meiosis I; type II: failure of meiosis II; type III: duplication of the genome of a mature gamete; type IV: no meiosis; and type V: fusion of two different ova), but those of other GCTs remain elusive. In this study, we analyzed 84 GCTs of various pathologic types to identify the histogenesis using single‐nucleotide polymorphism array by analyzing copy‐neutral loss of heterozygosity (CN‐LOH) and copy number alterations (CNAs). We detected types I and II in ovarian teratomas, type III in ovarian teratomas and yolk sac tumors (YSTs), and type IV in all GCT types. The GCTs with multiple‐type histogenesis (I–IV) (ovarian mature/immature teratomas and YST) show meiotic CN‐LOH with scant CNAs. Type IV‐only GCTs are either with mitotic CN‐LOH and abundant CNAs (seminoma, dysgerminoma, testicular mixed GCTs) or with scant CNAs and no CN‐LOH (pediatric testicular and mediastinal teratomas). The development sequences of CN‐LOH and CNA are different between the multiple type (I–IV) GCTs and type IV‐only GCTs. We analyzed two different histologic areas in eight GCTs (one mature teratoma with a mucin‐secreting adenoma, two immature teratomas, and five mixed GCTs). We found that GCTs (mature teratoma, immature teratoma, and mixed GCT) showed different genomic alterations between histologic areas, suggesting that genomic differences within a GCT could accompany histologic differentiation. Of note, we found evidence for collision tumors in a mixed GCT. Our data indicate that GCTs may have various histogenesis and intratumoral genomic differences, which might provide important information for the identification of GCTs, especially for those with different histologic areas. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Immune‐related gene expression signatures: a step forward in the stratification of patients with ovarian clear cell carcinoma †

Abstract Clear cell carcinoma of the ovary (CCC) is one of the five major histological types of ovarian cancer and presents specific clinicopathological features, such as a higher prevalence in the Asian population and a poor response to conventional chemotherapy. In a recent publication in The Journal of Pathology , Heong, Tan, Miwa et al demonstrated the heterogeneity of the immune landscape of CCC. They reported the immune signatures observed in a large cohort of CCC, including tumours from both Asian and Caucasian women. The authors analysed three cohorts from Europe, Japan, and Singapore, with a total of 246 tumours, and evaluated 730 immune‐related genes using NanoString technology. The study revealed four main transcriptional subtypes characterised by the expression of specific sets of genes: PD1‐high (11%), CTLA4‐high (29%), antigen‐presentation (42%), and a pro‐angiogenic subtype (18%). The two main conclusions of the study were: (1) that CCCs in women of Asian and Caucasian descent share significant molecular similarities, since all four molecular signatures are present in all the cohorts analysed, without any evident differences in frequency; and (2) that the PD1‐high and CTLA4‐high subtypes were associated with worse clinical outcomes and may be useful when stratifying treatment in early‐stage tumours. The immune signature could represent a promising biomarker of immunotherapy response if future prospective studies confirm it. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Molecular evidence of a clonal relationship of synchronous/multifocal gastric‐type lesions of the female genital tract

Abstract Synchronous/multifocal gastric‐type lesions (SMGLs) of the female genital tract are heterogeneous diseases that are rare and challenging to diagnose. The core issue is distinguishing between multiple primaries and multifocal metastases from a single lesion. This is vital for staging, prognosis, and treatment decisions, especially when metastases mimic primary and early lesions at the relevant sites. Traditional morphological diagnosis often faces a paradoxical situation on this key issue and cannot quantitatively evaluate the correlations among multiple foci. Here, six cases of SMGL were collected, two of which exhibited pagetoid dissemination within the genital tract, with all lesions being noninvasive. A total of 24 samples were subjected to whole‐exome sequencing. By inference based on overlapping genetic variations, base substitution mutation patterns, composition and similarity of COSMIC signatures, clonality indices, and the construction of evolutionary trees, it was inferred that the multiple foci in each patient were clonally related, indicating that all cases were metastatic. The follow‐up duration ranged from 7 to 62 months (median: 24.5 months). Four patients died of disease (median survival time: 24.5 months, range: 8–47 months), including one patient who had no invasive lesions at initial diagnosis; two patients experienced recurrences at 17 and 40 months, respectively. These results imply that even if all foci exhibit the appearance of in situ or premalignant changes histologically, they may actually be aggressive. Hence, for SMGLs, before opting for conservative treatment, comprehensive clinical assessment, appropriate surgical extent, adequate sampling, and careful microscopic examination are crucial. Clonal analysis should also be conducted where necessary to avoid undertreatment due to understaging. The study further explored the genomic traits of SMGLs involving more than two sites. © 2025 The Pathological Society of Great Britain and Ireland.

Single‐nucleus RNA sequencing identifies a novel tenogenic heterologous differentiation in endometrial carcinosarcomas: implications for diagnosis and tumor classification

Abstract Carcinosarcomas (CSs) are aggressive biphasic tumors characterized by epithelial and mesenchymal components, whose histogenesis and differentiation dynamics remain poorly understood. We present single‐nucleus RNA sequencing (snRNA‐seq) analysis of six CSs (five endometrial and one ovarian) and two normal endometrial samples, profiling over 96,298 cells. By integrating transcriptomic data with inferred copy number variations (CNVs), immunohistochemistry (IHC), fluorescence in situ hybridization (FISH), and in situ hybridization (ISH) validation, we resolved the complex cellular architecture of these tumors, identified lineage‐specific programs, and revealed unexpected differentiation trajectories. snRNA‐seq was used to further refine the histopathological classification of three cases by uncovering heterologous differentiation not previously recognized: one rhabdomyogenic, one osteogenic, and, notably, one exhibiting a novel tenogenic program, defined by the expression of SCX , MKX , and TNMD . All CSs displayed a prominent mesenchymal compartment comprising both undifferentiated fibroblast‐like cells and distinct lineage committed populations, including rhabdomyoblasts (Rhab), tenoblasts (Teno), osteoblasts (Osteo), and chondroblasts (Chond). In some tumors, multiple mesenchymal identities co‐existed, and in others, differentiation gradients (e.g. immature versus mature rhabdomyoblasts) were observed. These patterns underscore the cellular plasticity and multilineage potential of the sarcomatous component. Furthermore, the expression of specialized interface markers ( COL22A1 , NCAM1 , ACAN , CHRNG , MUSK ) suggests that some tumors use structured developmental programs reminiscent of the muscle–tendon junction, enthesis, or neuromuscular junction. CNV analysis revealed tumor‐specific genomic alterations with clonal and subclonal patterns linked to differentiation state, which were validated by FISH. Altogether, this study demonstrates that CSs are not static biphasic tumors but rather complex ecosystems with extensive developmental plasticity. Our findings redefine their classification and support the use of single‐nucleus approaches to uncover hidden differentiation trajectories in highly heterogeneous cancers, including the discovery of a previously unreported tenogenic lineage. Our results challenge the diagnosis of homologous CS when only morphological criteria are applied. © 2026 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Delta‐like 1 homolog ( DLK1 ) regulates cancer stemness and chemoresistance of ovarian cancer by CD44 / CD133 upregulation

Abstract Ovarian cancer is a heterogeneous gynecologic malignancy, with most cases diagnosed at an advanced stage. Despite the availability of effective treatments such as surgery and platinum/taxane‐based chemotherapy, advanced ovarian cancer frequently recurs, highlighting the need to investigate mechanisms of chemotherapy resistance. Delta‐like non‐canonical Notch ligand 1 (DLK1), a transmembrane protein of the EGF‐like family, is aberrantly expressed in several cancers. Our previous study demonstrated that DLK1 promotes oncogenic behaviors and epithelial–mesenchymal transition in ovarian high‐grade serous carcinoma. In this study, we observed a positive correlation between DLK1 and stemness markers CD44 and CD133 in human epithelial ovarian cancer using tissue microarray analysis. Overexpression of DLK1 by an adenovirus vector accelerated sphere‐forming capability and upregulated CD44, CD133, and ABCG2 expression in human ovarian cancer cell lines. Conversely, DLK1 silencing by siRNA abolished the stimulatory effects on the stem cell‐like properties and reduced CD44 and CD133 expression in ovarian cancer cells. Furthermore, DLK overexpression by an adenovirus vector enhanced colony formation and suppressed the cisplatin‐ and taxol‐induced death in human ovarian cancer cells. Conversely, DLK1 siRNA reversed cell death and colony formation induced by these chemotherapeutic agents. Finally, we demonstrated that DLK1 regulates CD44, CD133, and ABCG2 expression through the Notch1/AKT/STAT3 signaling pathway, involving the phosphorylation and translocation of STAT3. Collectively, these results suggest that targeting DLK1 may represent a potential therapeutic strategy to improve outcomes in recurrent ovarian cancer following chemotherapy. © 2026 The Pathological Society of Great Britain and Ireland.