Mesonephric-like adenocarcinoma: A single-institution experience.

e17657 Background: This study examines Mesonephric-like adenocarcinoma (MLA), a rare gynecologic malignancy, by comparing clinical characteristics, treatment approaches, and outcomes between ovarian/peritoneal (MLA-O) and endometrial (MLA-E) MLA to highlight differences in disease behavior and prognosis. Methods: A retrospective review of patients with a diagnosis of MLA-O or MLA-E, who were treated or received treatment planning at The University of Texas MD Anderson Cancer Center between January 1, 2000, and December 31, 2023. Central review by gynecologic pathologist was performed to confirm the histologic diagnosis of MLA. Data on demographics, disease stage, clinical treatments and recurrence/survival outcomes were extracted from medical records. Frequencies and percentages were calculated as needed to describe the study population. Results: : A total of 68 patients were diagnosed with MLA: 29 MLA-O and MLA-E. The median age at diagnosis was 57.8 years for the MLA-O group and 58.7 years for MLA-E group (p=0.7). Compared with the MLA-E group, the MLA-O group was more associated with more mixed histologic components (mainly endometrioid) (44.8% vs 17.9%, p=0.03), history of endometriosis (58.6% vs 15.4%, p=0.0006) Advanced-stage disease (stage III/IV) was more frequent in MLA-E group compared to MLA-O group (53.8% vs 37.9%; p=0.003). Neoadjuvant chemotherapy was used in 10.3% of MLA-O (3/29) and 12.8% of MLA-E cases (5/39). Primary surgery was performed in most followed by adjuvant chemotherapy in 62.1% (18/29) of MLA-O and 46.2% (18/39) of MLA-E cases. Forty-seven patients experienced either progression (O/P: n=9 vs E: n=6) or recurrence (O/P: n=12 vs E: n=20) (), with E: n=15; O/P: n=4). ). The median time to first recurrence was 2.8 years (95% CI 2.0 – not reached) and 3.5 years (95% CI 2.1, 5.3) in the MLA-O and MLA-E groups, respectively. Conclusions: This study highlights the distinct clinical profiles and of MLA based on tumor location but show similar poor overall survival and recurrence outcomes. These findings emphasize the need for further investigation into optimal management and molecular characterization of this rare malignancy.