Familial adenomatous polyposis (FAP) is an autosomal dominant cancer predisposition syndrome. It is caused by germline mutations in the APC gene. Individuals affected with FAP are at increased risk of developing not only colorectal cancer but also other cancers, such as thyroid cancer, pancreatic cancer, hepatoblastoma, medulloblastoma, and desmoid tumors. Children, adolescents, and young adults with a family history of GI or one of the listed FAP-associated cancers should be tested for genetic predisposition and monitored closely by following ACG Clinical Guidelines and other recommendations. For GI tract monitoring, sigmoidoscopy or colonoscopy are recommended every 1 to 2 years starting at age 10. Polyps serially obtained from these regular visits can be molecularly analyzed and compared with clinical outcomes. Such correlative data can help elucidate molecular profile changes that coincide with or precede increases in tumorigenic events and progression. Identified molecular profile changes (e.g. over-expression of certain genes) in polyps can be compared with those in peripheral blood samples (such as plasma derived cfDNA) to establish molecular biomarkers for progression.