A 40-year-old man has familial adenomatous polyposis (FAP) with >100 colonic polyps. He undergoes restorative proctocolectomy with ileal pouch-anal anastomosis (IPAA). The desmoid tumour risk, which is the leading cause of non-cancer death in FAP, is associated with:
- A APC mutation at codon 1309 (extreme 3' end)
- B MUTYH biallelic mutation
- C APC mutation in the desmoid region (codons 1310–2011, particularly 1444–1580) ✓
- D APC mutation at codon 463 only
Correct answer: C. APC mutation in the desmoid region (codons 1310–2011, particularly 1444–1580)
Explanation
Desmoid tumours in FAP are associated with APC mutations in the desmoid region (codons 1310–2011, particularly the segment around codons 1444–1580) and are strongly associated with abdominal surgery and family history. Mutations at codon 1309 are associated with severe attenuated polyposis phenotype. MUTYH mutations cause MAP (MUTYH-associated polyposis), a separate entity. Desmoids complicate 10–20% of FAP cases and can cause bowel obstruction, ureteric compression, or vascular encasement.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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