APC and Familial adenomatous polyposis: Based on the number of colorectal polyps (CPs), age of CP onset, and extracolonic manifestations, APC-associated polyposis includes two main clinical phenotypes, i.e., classical FAP, which is characterized by the early onset of more than 100 colorectal adenomatous polyps, and attenuated FAP (AFAP), which is characterized by the development of fewer colorectal adenomatous polyps (<100) and a later onset of clinical manifestations [6].