Alexander J Neil

Molecular and immunohistochemical characterization of ERBB2 activating mutations in low‐grade serous ovarian carcinoma

AimsLow‐grade serous carcinoma (LGSC) of the ovary presents unique therapeutic challenges due to its resistance to platinum‐based chemotherapies and a tendency to present at an advanced stage. Approximately 50% of LGSC possess activating mutations in KRAS, NRAS, and BRAF, a finding associated with better overall survival. However, many tumours lack obvious driver alterations against which to direct targeted treatment strategies, necessitating further investigation into molecular drivers of LGSC and their impact on clinical outcomes.Methods and ResultsWe conducted a retrospective analysis of 84 LGSC patients who underwent tumour‐only targeted next‐generation sequencing at our institution. Molecular data were correlated with clinical outcomes, HER2 immunohistochemistry, and supplemented with additional tumour sequencing data from the AACR GENIE cohort v15.1 (n = 295). Approximately 5% of LGSC cases across the combined cohort harboured activating alterations in ERBB2 (n = 17/369), which encodes the HER2 receptor tyrosine kinase. These alterations were mutually exclusive of other MAP kinase pathway mutations and included exon 20 insertions (n = 6), extracellular domain/transmembrane domain missense alterations (n = 4), and exon 16 skipping mutations (n = 7). ERBB2 exon 16 emerged as a mutational hotspot in LGSC when compared to other tumour types. Immunohistochemistry revealed variable HER2 expression patterns that were independent of ERBB2 mutational status. In our institutional cohort, patients with RAS/RAF mutant tumours (n = 38) showed better overall survival compared to RAS/RAF wildtype tumours (n = 35). No tumours in our internal cohort (n = 84) harboured ERBB2 amplifications.ConclusionAs the landscape of HER2‐directed therapies continues to evolve, these findings suggest that ERBB2 alterations and HER2 expression may represent a potential therapeutic target in LGSC.

Pattern A endocervical adenocarcinomas with ovarian metastasis are indolent and molecularly distinct from destructively invasive adenocarcinomas

AimsThe invasive pattern in HPV‐associated endocervical adenocarcinoma (HPVA) has prognostic value. Non‐destructive (pattern A) HPVA has excellent prognosis mirroring adenocarcinoma in‐situ (AIS). However, the rare occurrence of ovarian spread in these tumours suggests aggressiveness in a subset of patients with these otherwise indolent lesions. We hypothesise that AIS/pattern A HPVA with ovarian metastases are biologically different than metastatic destructively invasive HPVA.Methods and resultsSamples from patients with HPVA and synchronous or metachronous metastases were retrieved and reviewed to confirm diagnosis and determine the Silva pattern in the primary lesion. For each case, normal tissue, cervical tumour and at least one metastasis underwent comprehensive sequencing using a 447‐gene panel. Pathogenic single‐nucleotide variants and segmental copy‐number alterations (CNA), tumour mutational burden and molecular signatures were evaluated and compared between primary and metastases and among invasive pattern categories. We identified 13 patients: four had AIS/pattern A primaries, while nine had pattern B/C tumours. All AIS/pattern A lesions had metastasis only to ovary; 50% of patients with ovarian involvement, regardless of invasive pattern, also had involvement of the endometrium and/or fallopian tube mucosa by HPVA. In the ovary, AIS/pattern A HPVA showed deceptive well‐differentiated glands, often with adenofibroma‐like appearance. Conversely, pattern C HPVAs consistently showed overt infiltrative features in the ovary. Sequencing confirmed the genetic relationship between primary and metastatic tumours in each case. PIK3CA alterations were identified in three of four AIS/pattern A HPVAs and three of eight pattern B/C tumours with sequenced metastases. Pattern C tumours showed a notably higher number of CNA in primary tumours compared to pattern A/B tumours. Only one metastatic AIS/pattern A HPVA had a novel pathogenic variant compared to the primary. Conversely, five of eight pattern B/C tumours with sequenced metastases developed novel pathogenic variants in the metastasis not seen in the primary. All four AIS/pattern A patients were alive and free of disease at 31, 47, 58 and 212 months after initial diagnosis. Conversely, cancer‐related death was documented in five of nine pattern B/C patients with follow‐up at 7, 20, 20, 43 and 87 months.ConclusionMorphologically and genomically, AIS/pattern A HPVA with secondary ovarian involvement appears distinct from destructively invasive tumours. In at least a subset of these cases, ovarian spread appears to occur via trans‐Mullerian superficial extension, different from the stromal and lymphatic vascular spread typical of more aggressive tumours (pattern C). These differences may explain the indolent outcome observed in the rare subset of patients with AIS/pattern A HPVA and ovarian metastasis. Our data underscore the potential for conservative surgical management approaches to pattern A HPVA.