Patients’ FAP-related features
All patients harbored a pathogenic germline variant of the APC gene that was responsible for a truncated protein in five cases and the complete loss of the protein in one. Two of the 6 patients were probands, and FAP was diagnosed after the onset of gastrointestinal symptoms (8 years after treatment for MBL in one case). The other four patients belonged to families with already genetically determined polyposis. Two patients underwent total colectomy with IRA, while four have yet to undergo surgery. One of the patients who had total colectomy developed an intra-abdominal desmoid tumor 4 years after this prophylactic surgery.
Patients’ FAP-related family histories are shown in Table 3. Five of the 6 patients had a family history of polyposis, three had a family history of CRC, and none of the patients had a family history of CNS tumors. Other tumors were described in the families of three patients.