Mesonephric-Like Adenocarcinoma of the Endometrium and the Impact of the Updated 2023 FIGO Staging System.

Mesonephric adenocarcinomas are rare neoplasms derived from remnants of the paired mesonephric ducts. Neoplasms arising from the uterine corpus that are morphologically and immunohistochemically similar to true mesonephric carcinomas, but do not arise from mesonephric remnants, are termed "mesonephric-like" adenocarcinomas. The diagnosis of mesonephric-like adenocarcinoma is pathologically challenging. These tumors often exhibit a mixture of morphologic patterns of more common adenocarcinomas. Although their morphologic, immunohistochemical, and molecular profiles have been recently defined, much remains unknown about mesonephric-like adenocarcinomas. A better understanding of mesonephric-like andenocarcinoma's pathogenesis and molecular classification is needed to improve diagnosis and guide management of this rare and aggressive subtype of endometrial cancer. An updated International Federation of Gynecology and Obstetrics (FIGO) staging system for endometrial carcinoma was introduced in June 2023, upstaging aggressive histological subtypes such as mesonephric-like adenocarcinoma. In this report, we describe a patient with mesonephric-like adenocarcinoma arising in the uterine corpus, highlight the clinical significance of 2023 FIGO restaging, and discuss the multidisciplinary approach to treatment.