Interestingly, whereas tumors in the colon rectum occur invariably in almost 100% of subjects with APC germline mutations, with no prevalence for any sex and with the same incidence in males and in females (and in most colorectal polyps or cancers, there is a complete loss of the APC function documented by the high rate of LOH for APC in the tumoral tissue), FAP associated FNMTC occurs in a minority of affected siblings, in the absence of LOH for APC [6] and almost invariably in the female sex [26]. Here, FAP is linked to familial papillary or follicular thyroid carcinoma.