Michaela Kendall Bártů

Folate receptor alpha ( FRα ) expression in tubo‐ovarian and endometrial tumors: a study of 923 cases

Abstract Folate receptor alpha (FRα) is a promising therapeutic target due to its high expression in several tumor types and its rare expression in healthy tissue. Recently, the antibody‐drug conjugate mirvetuximab soravtansine has been approved for treatment of advanced platinum‐resistant high‐grade serous carcinoma (HGSC). Immunohistochemical expression of FRα has been extensively studied in HGSC, but most studies conducted before the clinical studies targeting FRα used variable antibodies and scoring criteria, which makes comparison of older literature data with recent studies difficult. Moreover, the data regarding its expression in other types of ovarian and other female genital tract tumors are limited or absent. In our study, we focused on immunohistochemical expression in 923 tubo‐ovarian and endometrial tumors (assessed on tissue microarrays), using standardized scoring criteria and the VENTANA FOLR1 CDx assay. The results of our study showed the highest FRα expression in serous carcinomas, specifically HGSC (45% positive cases), followed by low‐grade serous carcinoma (25%), endometrial serous carcinoma (11%), and serous borderline tumor (10%). Endometrioid and clear cell ovarian carcinomas showed rare positivity (2% and 1%, respectively). All other tumors examined were negative, including mucinous ovarian tumors, sex cord‐stromal tumors, endometrial endometrioid carcinomas, undifferentiated and dedifferentiated carcinomas, and endometrial clear cell carcinomas. In conclusion, these results confirm that FRα expression in HGSC and LGSC reaches similar values compared to published data, and is present in a minority of endometrial serous carcinomas. In other ovarian and endometrial tumors examined, FRα expression is absent or rare.

Immunohistochemical analysis of 147 cases of low-grade endometrial stromal sarcoma: refining the immunohistochemical profile of LG-ESS on a large, molecularly confirmed series

Abstract Low-grade endometrial stromal sarcoma (LG-ESS) can present diagnostic challenges, due to its overlapping morphological features with other uterine mesenchymal tumors. Misdiagnosis rates remain significant, and immunohistochemical data for LG-ESS are limited to small series and inconsistent antibody panels. This study aimed to refine the IHC profile of LG-ESS by analyzing a large, molecularly confirmed series of 147 cases using a panel of 24 antibodies, including newer markers like transgelin and smoothelin. CD10 and IFITM1, key endometrial stromal markers, were expressed in 86% (92% of those extensively) and 69% (60% of those extensively) of cases, with fusion-positive tumors showing significantly higher expression. Smooth muscle markers (α-SMA, desmin, h-caldesmon, calponin, transgelin) were variably expressed, predominantly in focal or low-intensity patterns, with α-SMA reaching the highest frequency of expression (44%). However, the intensity of smooth muscle marker expression was usually very low. Smoothelin was rarely expressed. Hormone receptors were frequently positive, with PR showing a higher frequency (92% vs. 83%) and intensity than ER. Markers like S-100, HMB45, and CD117 were largely negative; all tumors were p53 wild-type, with preserved SMARCB1/SMARCA4 expression and ALK and ROS1 negativity. This work represents the largest molecularly validated IHC study on LG-ESS, providing a robust diagnostic profile for routine pathology. By addressing key diagnostic limitations and examining newer markers, our study supports a more standardized approach to diagnosing LG-ESS and underscores the value of immunohistochemical panels, particularly in fusion-negative tumors where diagnosis relies on morphological and immunohistochemical interpretation. These findings contribute critical data for improving diagnostic accuracy.

Endometrial stromal tumor with whorling and GREB1::CTNNB1 fusion—a case report on a rare entity

Endometrial stromal tumors are rare lesions with a diverse morphology, which may make achieving the correct diagnosis challenging in some cases. We report a case of a uterine mesenchymal tumor diagnosed as endometrial stromal nodule with a peculiar whorled morphology and GREB1::CTNNB1 fusion confirmed by transcriptome RNA sequencing. The tumor was sharply demarcated, lacked invasive growth, and had benign behavior, as the patient remained without disease recurrence 15 years later. Immunohistochemically, the tumor cells showed diffuse nuclear expression of beta-catenin, confirming the activation of the beta-catenin pathway. Our case represents only the 4th reported case of CTNNB1-rearranged endometrial stromal tumor with extensive whorling. The biological nature of uterine tumors characterized by whorled morphology and rearrangement of CTNNB1 is not yet clear, which underscores the importance of genetic profiling for accurate diagnosis and potential targeted therapies in malignant cases.

HER2 status as a potential predictive biomarker for ovarian clear cell carcinoma

Ovarian clear cell carcinoma (OCCC) is a subtype of ovarian carcinoma characterized by unique biological features and highly malignant characteristics including low chemosensitivity. Therefore, new therapeutic targets are needed. These could include the downstream pathways of receptor tyrosine kinases, especially the human epidermal growth factor receptor 2 (HER2). Our main objective was to characterize the HER2 status using immunohistochemistry (IHC) and FISH on 118 OCCCs, also considering the novel paradigm of HER2-zero and HER2-low status. Other aims included determination of the association between HER2 status and survival, HER2 gene DNA and RNA NGS analysis, HER2 gene expression analysis, and correlation between IHC and gene expression in HER2-zero and HER2-low cases. Cases with HER2 overexpression/amplification accounted for 5.1% (6/118), with additional 3% harbouring HER2 gene mutation. The remaining 112 (94.9%) cases were HER2-negative. Of these, 75% were classified as HER2-zero and 25% as HER2-low. This percentage of HER2 aberrations is significant concerning their possible therapeutic influence. Cases from the HER2-zero group showed significantly better survival. Although this relationship lost statistical significance in multivariate analysis, the results have potential therapeutic significance. HER2 gene expression analysis showed a significant correlation with HER2 IHC status in the entire cohort (HER2-positive vs. HER2-negative), while in the cohort of only HER2-negative cases, the results did not reach statistical significance, suggesting that gene expression analysis would not be suitable to confirm the subdivision into HER2-low and HER2-zero. Our results also emphasize the need for standardized HER2 testing in OCCC to determine the best predictor of clinical response.