FAP and attenuated familial adenomatous polyposis: Since APC/MUTYH-negative cases are noticeably enriched in AFAP patients, while the mutation positive group in classical FAP cases, we also compared age of onset data separately for the FAP and AFAP groups, and found no significant difference between mutation negative and positive cases (p = 0.18 for the AFAP and p = 0.3 for the FAP group).