Less than one-third of CRC cases with MMRdeficiency (dMMR)/MSI-H have germline mutations in MMR genes(MLH1, MSH2, PMS2, andMSH6) which are linked to an inherited condition of cancersusceptibility called Lynch syndrome.8 International guidelines recommend testing for MMR status in all patientswith CRC to inform the need for cascade testing of family members and subsequentrisk-reduction strategies in those identified with Lynch syndrome.(Table 3). The gene discussed is MLH1; the disease is colorectal carcinoma.