Inactivation of the DNA MMR genes (MLH1, MSH2, or more rarely MSH6 and PMS2) predisposes carriers to multiple malignancies, including early-onset colorectal and endometrial cancer, or less frequently ovarian, small bowel, urothelium, biliary tract, and gastric cancers [1,2]. The gene discussed is MSH2; the disease is endometrial cancer.