Mesonephric Adenocarcinoma of the Uterine Corpus: A Case Report and Diagnostic Pitfall.

Mesonephric adenocarcinoma is a rare tumor type that is usually found in areas where the Wolffian duct was present during the fetal period. We report a case of mesonephric adenocarcinoma of the uterine corpus in a 66-year-old woman who presented with vaginal bleeding. Pelvic magnetic resonance imaging revealed a 2.7-cm-sized irregular thickening and enhancement of the uterine body. The diagnosis following endometrial curettage biopsy was endometrioid adenocarcinoma, and the patient underwent a total hysterectomy with bilateral salpingo-oophorectomy. The tumor was composed of small tubular and ductal components, and a retiform appearance was also observed in the deeper areas. The tumor cells were immunopositive for cytokeratin, vimentin, CD10 with a luminal staining pattern, PAX2, and PAX8, and immunonegative for estrogen receptor and progesterone receptor, which was consistent with tumor of mesonephric origin. Mesonephric neoplasms reveal relatively low-grade nuclear feature, characteristic immunoprofiles (immunonegative for ER and PR, and immunopositive for CD10, PAX2, PAX8, and GATA3), and unique tumor location (myometrium), whereas Müllerian neoplasms such as endometrial adenocarcinoma show various morphology, immunopositivity for ER and PR, and primarily endometrial location. As described above, an integration of the clinical features, morphologic characteristics, and immunohistochemical profiles is needed to make a diagnosis.