Testing with a 7-gene high-risk hereditary colon cancer panel identified a homozygous pathogenic variant, c.1187G>A (p.Gly396Asp) in MUTYH, and a likely pathogenic duplication of exon 7 in MSH2. Since this test result, the proband's mother was diagnosed with colon cancer; subsequent genetic testing confirmed she also carries the likely pathogenic duplication in the MSH2 gene. This evidence concerns the gene MUTYH and malignant colon neoplasm.