A clear genotype–phenotype relationship exists: APC mutations between codons 1445 and 1578 are associated with an increased risk of desmoid tumors—patients with attenuated FAP usually have mutations at the 5′ (proximal to codon 1517) or the 3′ end (distal to codon 1900) of the APC gene. Here, APC is linked to desmoid tumor.