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

Clinicopathologic and Molecular Characterization of Gynecologic Carcinosarcomas With a Mesonephric-Like Carcinomatous Component

Carcinosarcoma with a mesonephric-like carcinomatous component (MLCS) is a rare subtype of gynecologic malignancy recently described in the literature. This study aims to expand the genomic characterization of MLCS by performing independent molecular analysis of the carcinomatous and sarcomatous components in a series of MLCS. Eight cases of gynecologic MLCS (endometrial, lower uterine segment, and ovarian) were identified and underwent clinicopathologic evaluation. Genomic DNA extraction and next-generation sequencing (NGS) were performed separately from the carcinomatous and sarcomatous components of 4 tumors, while 2 tumors underwent NGS of combined carcinomatous and sarcomatous components. The average age at diagnosis was 65.6 years (range 50 to 83 years). MLCS patients were diagnosed at FIGO stage I (n=3), stage II (n=2), stage III (n=2), and stage IV (n=1). The carcinomatous and sarcomatous components were observed to harbor the same single nucleotide variations. All cases had less than 10 mutations/Mb and were microsatellites stable. All cases (6/6, 100%) harbored KRAS point mutations in codon 12, including the following variants: p.G12D (n=2), p.G12A (n=2), and p.G12V (n=2). Five cases showed additional alterations in ARID1A (case 1), PTEN (case 2), PIK3CA (case 4), SPOP (case 6), TET1 (case 6), BUB1 (case 7), LYN (case 7) and PTPRD (case 7). The presence of both KRAS and PTEN / PIK3CA alterations suggests a combined endometrioid and mesonephric differentiation in MLCS.

Papillary and ductal patterns of mesonephric-like adenocarcinomas are often overlooked: a retrospective revaluation of over 1000 endometrial carcinomas

AIMS

Mesonephric-like adenocarcinoma (MLA) of the endometrium is often a diagnostic challenge, due to its morphological resemblance to other more common Müllerian neoplasms. This study aimed to retrospectively identify overlooked MLA in a large endometrial carcinoma cohort, using a combination of immunohistochemistry (IHC), morphology and KRAS sequencing.

METHODS AND RESULTS

IHC was conducted on 1094 endometrial carcinomas, identifying 16 potential MLA cases based on GATA3+ and/or TTF1+ and ER- staining patterns, which subsequently underwent detailed histological review, KRAS sequencing and ProMisE molecular classification. Of the IHC screen-positive cases, one was positive for both GATA3 and TTF1, nine were positive for GATA3 only and six were positive for TTF1 only. All IHC screen-positive cases were POLE wild-type. All five tumours in the NSMP category showed morphological features of MLA, while the three MMRd and eight p53abn tumours did not show MLA morphology. The five cases diagnosed as MLA on review were all originally diagnosed as low-grade endometrioid adenocarcinoma probably because of rare morphological patterns, being predominantly papillary or ductal. Four of the five cases harboured a KRAS mutation.

CONCLUSION

This study highlights the importance of a comprehensive diagnostic approach for accurately identifying endometrial MLA and for pathologists to be aware of papillary and ductal patterns in endometrial carcinoma assessment. Further exploration into the molecular landscape of MLA is essential for refining diagnostic criteria and developing targeted therapies.

Cellular origins of mucinous ovarian carcinoma

Mucinous 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.

Mesonephric-like adenocarcinoma of the female genital tract: Pathologic diagnosis, clinical outcomes, and novel therapeutics

In 2016, McCluggage and colleagues first defined mesonephric-like adenocarcinoma (MLA) of the uterus and extra-uterine sites. Following this initial description, the World Health Organization officially recognized MLA as a type of uterine and ovarian carcinoma and subsequent studies have further refined the morphologic definition, immunohistochemical profile, molecular underpinnings, and clinical behavior in this rare entity. A consortium of pathologists, gynecologic oncologists, medical oncologists, radiation oncologists, as well as basic science collaborators with expertise in MLA was convened to develop consensus regarding the pathologic diagnosis, and to identify unanswered questions and priority areas for research. Here, we review the current understanding of MLA from a pathologic, molecular, and clinical standpoint.

FOLR1 as a therapeutic target in platinum-resistant ovarian carcinoma: unique expression patterns across ovarian carcinoma histotypes and molecular subtypes of low-grade serous carcinoma

OBJECTIVE

With the development of novel antibody-drug conjugates (ADCs), folate receptor alpha (FOLR1) is a promising therapeutic target for the treatment of platinum-resistant tubo-ovarian carcinomas. The main aims of this study were to assess FOLR1 protein expression in a large cohort of ovarian carcinoma histotypes. To inform future clinical trial design we identified molecular correlates of FOLR1 expression in low-grade serous carcinoma (LGSC).

METHODS

One thousand five hundred forty-seven ovarian carcinoma samples from 5 different Canadian cohorts were successfully evaluated by immunohistochemistry for FOLR1 expression using the PS2+ system. Statistical analyses with clinicopathological parameters, LGSC molecular subtypes, and overall survival (OS) were performed.

RESULTS

High FOLR1 expression was detected in 44% of high-grade serous carcinomas, and in 30% LGSC, 8% clear cell, 6% endometrioid, and 0% mucinous and/or mesonephric-type adenocarcinomas. In 160 LGSC cases, FOLR1 expression was more frequent in cases with normal MAPK pathway status (37% MAPK wild type vs. 14% canonical MAPK pathway mutations; p=0.002), low progesterone receptor (PR) expression (41%) vs. 23% (Allred score >2; p=0.02), and p16 loss (48% p16 absent vs. 26% normal; p=0.03). Canonical MAPK mutation status and PR expression remained significant on multivariable analysis. No significant associations between OS and FOLR1 expression were observed.

CONCLUSION

A significant proportion of LGSC express high FOLR1 levels supporting the development of clinical trials to investigate ADCs targeting FOLR1 as novel agents for treating this disease. In LGSC, high FOLR1 expression was associated with fewer MAPK pathway alterations, low PR expression, and p16 loss.

Controversies in the Management of Mesonephric and Mesonephric-Like Adenocarcinomas of the Female Genital Tract

Mesonephric and mesonephric-like adenocarcinomas of the gynecologic tract are a rare subset of gynecologic tumors that are frequently associated with the presence of somatic KRAS mutations. Owing to their rare nature and ability to arise in different gynecologic sites, pathologic diagnosis is often challenging and under-represented. Immunohistochemistry and routine use of next-generation sequencing has allowed these cases to be more readily identified; however, there is still a paucity of clinical outcomes data, and the efficacy of treatment paradigms remains largely unknown. Historically, mesonephric and mesonephric-like adenocarcinomas were considered to be less responsive to systemic treatment, but response rates to first-line platinum-doublet chemotherapy for metastatic disease may be higher than initially suspected. Recurrent disease is often distant and located in the lungs, suggesting an important role of surveillance chest imaging. Given that most of these tumors are associated with somatic mitogen-activated protein kinase pathway mutations, a currently open phase II trial is assessing the dual RAF/MEK clamp avutometinib in combination with the FAK inhibitor defactinib in patients with recurrent mesonephric and mesonephric-like adenocarcinomas. Continued multi-institutional prospective trials are necessary to elucidate additional treatment options for these rare tumors.

STK11 Adnexal Tumor: Exploring the Association With Peutz-Jeghers Syndrome and its Distinction From Morphologic Mimickers

STK11 adnexal tumor is a novel malignant neoplasm of uncertain histogenesis frequently arising in a para-adnexal location and associated with Peutz-Jeghers syndrome in ∼50% of patients. Its broad morphologic spectrum and nonspecific immunohistochemical profile has resulted in misclassification in the past as a variety of other neoplasms including those of wolffian, sex cord-stromal, mesothelial, and epithelial derivation. This review focuses on the spectrum of adnexal neoplasms that may develop in Peutz-Jeghers syndrome, with particular emphasis on STK11 adnexal tumor and its differential diagnosis.

Ovarian Mesonephric-like Adenocarcinoma: Its Prevalence in a Japanese High-Volume Cancer Center and a Literature Review on Therapeutic Targets

BACKGROUND

Ovarian mesonephric-like adenocarcinoma (MLA) is a newly described histological type known for its aggressive behavior. This study aims to determine the frequency of ovarian MLA, review the existing literature, and elucidate its clinicopathological characteristics, including the potential therapeutic targets.

METHODS

We retrospectively reviewed the pathological diagnoses of 501 primary ovarian cancer surgical cases at our institution from 2010 to 2023. MLAs exhibiting typical morphological and immunohistochemical features were included. The frequency and clinicopathological characteristics of these cases were summarized. Additionally, we conducted a literature search using PubMed to collect and summarize previously reported cases of ovarian MLAs.

RESULTS

Among the 501 primary ovarian cancer cases, we identified 3 cases (0.6%) of MLA. The patients were 52-76 years old, and the initial FIGO stages were IC1 (two cases) and IIIB (one case). All the cases exhibited HRP, pMMR, PD-L1 negativity (CPS < 1), and low HER2 expression. Two cases experienced metastatic recurrence. A literature review identified 97 cases of MLA. The MLAs frequently exhibited KRAS mutations (90%, 38/42), with a recurrence rate of 39% (26/67).

CONCLUSION

MLAs accounted for 0.6% of malignant ovarian tumors at our institution, all of which were advanced or recurrent cases. These cases showed HRP, pMMR, and PD-L1 negativity, indicating a lack of current therapeutic targets. The literature also reported a high incidence of advanced and recurrent cases, highlighting the need for accurate diagnosis and the development of new treatments. The frequent KRAS mutations suggest a potential therapeutic target for recurrent or metastatic MLA.

Mesonephric-type adenocarcinomas of the ovary: prevalence, diagnostic reproducibility, outcome, and value of PAX2

Mesonephric-type (or -like) adenocarcinomas (MAs) of the ovary are an uncommon and aggressive histotype. They appear to arise through transdifferentiation from Müllerian lesions creating diagnostic challenges. Thus, we aimed to develop a histologic and immunohistochemical (IHC) approach to optimize the identification of MA over its histologic mimics, such as ovarian endometrioid carcinoma (EC). First, we screened 1,537 ovarian epithelial neoplasms with a four-marker IHC panel of GATA3, TTF1, ER, and PR followed by a morphological review of EC to identify MA in retrospective cohorts. Interobserver reproducibility for the distinction of MA versus EC was assessed in 66 cases initially without and subsequently with IHC information (four-marker panel). Expression of PAX2, CD10, and calretinin was evaluated separately, and survival analyses were performed. We identified 23 MAs from which 22 were among 385 cases initially reported as EC (5.7%) and 1 as clear cell carcinoma. The interobserver reproducibility increased from fair to substantial (κ = 0.376-0.727) with the integration of the four-marker IHC panel. PAX2 was the single most sensitive and specific marker to distinguish MA from EC and could be used as a first-line marker together with ER/PR and GATA3/TTF1. Patients with MA had significantly increased risk of earlier death from disease (hazard ratio = 3.08; 95% CI, 1.62-5.85; p < 0.0001) compared with patients with EC, when adjusted for age, stage, and p53 status. A diagnosis of MA has prognostic implications for stage I disease, and due to the subtlety of morphological features in some tumors, a low threshold for ancillary testing is recommended.

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

Mesonephric 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.