MRC1 and neoplasm: Somatic dMMR and MSI are also encountered in a variety of neoplasms.1 For instance, approximately 15% of sporadic colon carcinomas are dMMR, most commonly because of hypermethylation of the MLH1 promoter or double somatic mutations in MLH1 or other MMR genes.12,13 MMR status in sporadic neoplasms may also have prognostic significance, as exemplified by longer overall and disease-free survival in patients with dMMR CRC.14