Mesonephric-Like Adenocarcinoma: Two Cases Of A Rare Entity And Review Of Literature

Abstract Introduction/Objective Mesonephric-like adenocarcinoma (MLA) is a rare gynecologic malignancy occurring in the uterus and ovary and is morphologic similar to cervical mesonephric adenocarcinoma. We present two cases of mesonephric-like adenocarcinoma of the ovary. Methods The first case is a 72-year-old female presented with abdominal pain with bloating. Abdominal CT scan showed a 7.4 x 6.3 x 6.1 cm heterogenous right adnexal mass. The second case is a 66-year-old female with history of heavy bleeding and endometriosis, status post total abdominal hysterectomy with bilateral salpingo-oophorectomy 20 years ago. Abdominal CT scan demonstrated a 5.3 cm right pelvic mass and 12.5 cm right pelvic sidewall lymph node. Results Both tumors have characteristic variety of features including ductal, tubular, retiform, papillary, solid and infiltrative morphological patterns. Cytologic atypia is mild to moderate. The histological features can raise a broad differential diagnosis including primary tubo-ovarian carcinomas, sex cord-stromal tumors, and metastatic carcinomas. Immunohistochemical stains demonstrate the ovarian tumor cells are positive for multiple pan-epithelial markers (AE1/AE3); negative for sex cord-stromal markers (inhibin and calretinin); positive for PAX8, GATA3, TTF1, and CD10; and negative for ER, PR, and WT1. In the first case, a small incidental endometrial carcinoma arising from an endometrial polyp was also identified. Morphologically, it is distinct from the ovarian mesonephric-like adenocarcinoma. Conclusion Morphological and immunohistochemical features of the two tumors are consistent with MLA, a very rare ovarian tumor that is thought to arise either from mesonephric remnants in the para-ovarian tissue or by trans- differentiation from a benign or neoplastic Mullerian precursor. These tumors are reported to have a very high frequency of KRAS mutations followed by PIK3CA mutations. Due to their rarity, the clinical behavior of these tumors is unknown.