Evaluation of yield and experiences of age-related molecular investigation for heritable and nonheritable causes of mismatch repair deficient colorectal cancer to identify Lynch syndrome.

Universal mismatch repair deficiency (dMMR) testing of colorectal cancer (CRC) is promoted as routine diagnostics to prescreen for Lynch syndrome. We evaluated the yield and experience of age-related molecular investigation for heritable and nonheritable causes of dMMR in CRC below age 70 to identify Lynch Syndrome. In a prospective cohort of 3602 newly diagnosed CRCs below age 70 from 19 hospitals, dMMR, MLH1 promoter hypermethylation, germline MMR gene and somatic MMR gene testing was assessed in daily practice.