Familial adenomatous polyposis (FAP) and its variants Gardner syndrome

Familial adenomatous polyposis (FAP) and its variants (Gardner syndrome, Turcot syndrome, and attenuated familial adenomatous polyposis [AFAP]) account for less than 1 percent of CRCs.

Lynch syndrome or HNPCC is an autosomal-dominant syndrome that is more common than FAP and accounts for approximately 3 percent of all colonic adenocarcinomas.

The majority of patients with hereditary breast and ovarian cancer (HBOC) syndrome have mutations in either the breast cancer type 1 or 2 susceptibility gene (BRCA1 and BRCA2). HBOCs attributable to pathogenic variants in BRCA are characterized by an autosomal-dominant pattern of inheritance; markedly increased susceptibility to breast and ovarian cancers, with an especially early onset of breast cancer; and an increased incidence of tumors of other organs, such as the fallopian tubes, prostate, male breast, and pancreas

Patients with a personal history of CRC or adenomatous polyps of the colon are at risk for the future development of colon cancer. In patients undergoing resection of a single CRC, metachronous primary cancers develop in 1.5 to 3 percent of patients in the first five years postoperatively.

A reasonable estimate of the colon cancer incidence is approximately 0.5 percent per year for subjects with disease duration between 10 and 20 years, then 1 percent per year thereafter. Thank you.