An Ovarian Adenocarcinoma With Combined Low-grade Serous and Mesonephric Morphologies Suggests a Müllerian Origin for Some Mesonephric Carcinomas

Mesonephric carcinomas are rare adenocarcinomas of the female genital tract that occur most commonly in the uterine cervix. They are classically thought to arise from benign mesonephric remnants, and are rarely reported at other sites in the gynecologic tract. Here we present an interesting biphenotypic ovarian adenocarcinoma with intimately associated but distinct components of both low-grade serous carcinoma and mesonephric-like carcinoma. A serous borderline tumor was present adjacent to the invasive carcinoma, and no benign mesonephric precursors were identified. Numerous invasive peritoneal metastases were present, including multiple metastases with both low-grade serous and mesonephric-like elements. Consistent with recent reports, foci of mesonephric-like carcinoma were morphologically and immunohistochemically identical to classic mesonephric carcinoma of the cervix. On molecular analysis, the serous borderline tumor, primary and metastatic low-grade serous carcinoma, and primary and metastatic mesonephric-like carcinoma each harbored a shared NRAS p.Q61R hotspot mutation, shared gains in chromosome 1q and 18p, and shared losses in chromosomes 1p, 18q, and 22. These shared molecular features indicate a clonal relationship between all morphologic elements of this ovarian adenocarcinoma, suggesting that at least some mesonephric carcinomas may arise from Müllerian precursors.