Clinicopathologic and Molecular Characterization of Gynecologic Carcinosarcomas With a Mesonephric-Like Carcinomatous...

Carcinosarcoma with a mesonephric-like carcinomatous component (MLCS) is a rare subtype of gynecologic malignancy recently described in the literature. This study aims to expand the genomic characterization of MLCS by performing independent molecular analysis of the carcinomatous and sarcomatous components in a series of MLCS. Eight cases of gynecologic MLCS (endometrial, lower uterine segment, and ovarian) were identified and underwent clinicopathologic evaluation. Genomic DNA extraction and next-generation sequencing (NGS) were performed separately from the carcinomatous and sarcomatous components of 4 tumors, while 2 tumors underwent NGS of combined carcinomatous and sarcomatous components. The average age at diagnosis was 65.6 years (range 50 to 83 years). MLCS patients were diagnosed at FIGO stage I (n=3), stage II (n=2), stage III (n=2), and stage IV (n=1). The carcinomatous and sarcomatous components were observed to harbor the same single nucleotide variations. All cases had less than 10 mutations/Mb and were microsatellites stable. All cases (6/6, 100%) harbored KRAS point mutations in codon 12, including the following variants: p.G12D (n=2), p.G12A (n=2), and p.G12V (n=2). Five cases showed additional alterations in ARID1A (case 1), PTEN (case 2), PIK3CA (case 4), SPOP (case 6), TET1 (case 6), BUB1 (case 7), LYN (case 7) and PTPRD (case 7). The presence of both KRAS and PTEN / PIK3CA alterations suggests a combined endometrioid and mesonephric differentiation in MLCS.