In colorectal (CRCs) and endometrial cancers (ECs), tumour MMR-deficiency showing loss of MLH1 and PMS2 protein expression (MLH1/PMS2-deficiency) is predominantly caused by somatic MLH1 hypermethylation, however, it is not clear if somatic MLH1 hypermethylation is a cause of MLH1/PMS2-deficiency in sebaceous neoplasia. The gene discussed is MLH1; the disease is endometrial cancer.