Liu et al. (2003) screened index patients from 70 families with colorectal cancer for germline mutations in the MLH3 gene. None of the families had classical or attenuated familial adenomatous polyposis. Liu et al. (2003) identified 1 frameshift ... Liu et al. (2003) screened index patients from 70 families with colorectal cancer for germline mutations in the MLH3 gene. None of the families had classical or attenuated familial adenomatous polyposis. Liu et al. (2003) identified 1 frameshift mutation and 11 missense mutations in MLH3 in 16 of the 70 index patients (23%). Most of the mutations were found in low-risk patients, suggesting MLH3 to be a low-risk gene for colorectal cancer. Tumors in all index cases with MLH3 mutations were clearly microsatellite instability (MSI)-negative, suggesting that the mechanism in carcinogenesis is not likely to involve deficient mismatch repair (MMR). See 604395 for a discussion of somatic MLH3 mutation in colorectal and other cancers.