Lynch syndrome (LS) is caused by germline pathogenic variants (PVs) in one of the DNA mismatch repair (MMR) genes (MLH1, MSH2, MSH6, or PMS2) or by deletions in the epithelial cell adhesion molecule gene (EPCAM), which increases susceptibility to colorectal and endometrial cancers and other tumors (1–3). The gene discussed is PMS2; the disease is endometrial cancer.