True mixed ovarian carcinomas are uncommon, accounting for fewer than 1% of ovarian carcinomas. 1 They comprise carcinomas with two or more different histological types and are often associated with endometriosis. Ovarian mesonephric-like adenocarcinoma (MLA) was included in the WHO Classification of Tumours in 2020 and is considered to have aggressive clinical behaviour. Mixed ovarian carcinomas containing MLA are exceptionally rare, with six published case reports to date in the English literature. Previous case studies have reported ovarian MLA in association with low-grade serous carcinoma, high-grade serous carcinoma, endometrioid carcinoma and clear cell carcinoma, but not mucinous carcinoma. 2,3 We present a case of ovarian MLA with morphological areas of mucinous and endometrioid carcinoma, arising within a background of extensive endometriosis. Molecular testing demonstrated common mutations in KRAS G12V, ARID1A and gains in the 1q21.3-region in all three components. The presence of multiple clonal relationships greatly diminishes the possibility of a collision tumour and provides further evidence to support the concept that ovarian MLA is a Müllerian neoplasm with mesonephric transdifferentiation. We summarise the clinical, histological and molecular features of MLA and discuss some of the diagnostic considerations related to this rare entity.
Zhu et al. (Sun,) studied this question.