Synchronous Bilateral Ovarian Mesonephric-like Adenocarcinomas with Separate Origins from High-Grade Mullerian Adenosarcoma and Endometriosis: Report of a Rare Case.

Mesonephric-like adenocarcinoma (MLA) of the ovary is a recently recognized, rare malignancy with aggressive clinical behavior, and is thought to originate from Mullerian epithelium with mesonephric transdifferentiation. Emerging evidence suggests that MLA may be classified as an endometriosis-associated neoplasm. The presence of a sarcomatous component within MLA is extremely rare, with common differential diagnoses including the spindle cell component of MLA, carcinosarcoma, as well as mixed Mullerian adenocarcinoma and adenosarcoma. Herein, we report a 58-year-old Chinese woman with bilateral ovarian solid-cystic masses. The left ovarian mass comprised a biphasic tumor with a predominantly high-grade sarcomatous component displaying heterologous mesenchymal differentiation, including liposarcoma, rhabdomyosarcoma and chondrosarcoma-like areas, with a null-type p53 expression. The epithelial component ranged from a bland appearance in areas diagnostic of adenosarcoma to a clearly invasive carcinoma, both with mesonephric-like phenotype, being negative for estrogen receptor, progesterone receptor, and Wilms' tumor 1, variably positive for paired box gene 8, GATA binding protein 3, and thyroid transcription factor 1, with a wild-type p53 expression. The differing p53 expression between the epithelial and sarcomatous elements mitigated against a diagnosis of carcinosarcoma. The right ovarian mass showed endometriosis with focal direct evidence of the development of malignancy within a benign endometriotic cyst, exhibiting the identical immunoprofile of MLA but originating as another malignancy. To the best of our knowledge, this case represents the first reported case of synchronous bilateral ovarian MLAs with separate origins, from high-grade Mullerian adenosarcoma and endometriosis respectively, which broadens the morphologic spectrum of MLA and provides further evidence supporting the Mullerian origin theory.