Genetic tests in colon cancer

About 30% of colorectal cancers (CRCs) present a familial aggregation and 5% are hereditary forms. Main syndromes are: HNPCC or Lynch's syndrome, familial autosomal polyposis (FAP), polyposis associated to MUTYH (MAP). Diagnosis includes the identification of a germline mutation. HNPCC is caused by mutation of mismatch repair genes. The molecular evaluation starts with analysis of microsatellite instability (MSI), peculiar of HNPCC CRCs. If positive, the main genes (MSH2 and MLH1) should be tested. APC gene is defective in FAP; the screening test is the protein truncation test (PTT). MAP is due to point mutation of MUTYH gene. A genetic diagnosis aloows a maximized surveillance in these patients.