Mesonephric-Like Adenocarcinomas, an Underdiagnosed Rare Type of Gynecological Malignancy Associated with Aggressive Clinical Behaviors: A Series of 4 Patients from Single Institution

Mesonephric-like adenocarcinoma (MLA) is a newly recognized type of carcinoma that occurs in the uterus and ovaries. MLA exhibits distinct morphological and immunophenotypical features similar to those of mesonephric carcinoma of the cervix or vagina, with the majority of reported tumors containing KRAS mutations. MLA is exceedingly rare and appears to be associated with aggressive clinical behavior. Literature regarding the clinical behavior of MLAs remains limited. Here, we report four additional MLA patients with detailed morphological and immunophenotypical analysis, as well as clinicopathological and follow-up information. Additionally, molecular study was conducted on the ovarian MLA tumor and one uterine MLA tumor. Our findings support the observation that MLA is associated with an aggressive clinical course and poor clinical outcomes. Out of four tumors presented, 2 (50%) were at an advanced clinical stage, 3 (75%) presented with metastasis (including 2 (50%) with lung metastasis), and 2 (50%) patients died of the disease. MLA is often misdiagnosed as other types of gynecological carcinoma, as indicated in the literature and evidenced in our study, where 2 (50%) were initially misdiagnosed as low-grade endometrioid carcinoma in biopsy. Therefore, an integrated approach, including careful evaluation of the morphological and immunophenotypical features of the tumor, preferably with molecular confirmation, is critical for accurate diagnosis of this aggressive malignancy.