Dr. Britta Weigelt of MSKCC discusses her team’s study on synchronous endometrial (EC) and ovarian carcinomas (OC) in Lynch syndrome and constitutional Mismatch Repair Deficiency Syndrome (CMMRD). Contrary to sporadic synchronous ECs/OCs, which are almost invariably clonally related, ECs/OCs simultaneously involving the uterus and ovary in LS patients may represent two independent primary tumors. Like their sporadic counterparts, a subset of MMR deficiency syndrome-related synchronous ECs/OCs may also originate from a single with the endometrium being the likeliest site of origin. Associated article: Clonal relationship and directionality of progression of synchronous endometrial and ovarian carcinomas in patients with DNA mismatch repair-deficiency associated syndromes. https://www.nature.com/articles/s41379-020-00721-6