Synchronous Endometrial and Ovarian Endometrioid Carcinoma With MUTYH Germline Mutation: A Case Report With Genetic Analysis.

Synchronous endometrial and ovarian endometrioid carcinoma, which simultaneously involves the endometrium and ovary, is a relatively rare entity among gynecological cancers. Precise diagnosis and risk stratification are crucial for disease management. We present a unique case of a 40-year-old woman diagnosed with synchronous endometrial and ovarian endometrioid carcinoma carrying a monoallelic pathogenic MUTYH germline variant. Despite the histological morphology of the right ovarian tumor exhibiting some differences compared to the uterine tumor, we identified three identical somatic mutations shared between the uterine tumor and right ovarian tumor, along with four additional mutations exclusive to the uterine tumor, through the utilization of massively parallel sequencing of a 196-gene panel. These findings enabled us to elucidate the clonal relatedness and potential clonal evolution of the tumor across the two anatomical sites. Furthermore, in accordance with the 2023 FIGO staging system, the patient was diagnosed with Stage IIIB2 uterine cancer, and consequently, adjuvant radiation and chemotherapy were administered after surgery. She is being followed periodically and is normal 15 months after surgery. To the best of our knowledge, this study presents the first case of a patient with synchronous endometrial and ovarian endometrioid carcinoma harboring a monoallelic pathogenic MUTYH germline variant.