Neoplasia USMLE Step 1 Practice Question
A 45-year-old woman with a 20-year history of ulcerative colitis presents to her gastroenterologist with worsening abdominal pain, bloody diarrhea, and unintentional weight loss of 8 pounds over 3 months. Vital signs are stable. Laboratory studies show hemoglobin 9.8 g/dL and elevated carcinoembryonic antigen (CEA). Colonoscopy reveals a descending colon mass with surrounding strictures and multiple areas of intestinal metaplasia. Biopsy of the mass shows adenocarcinoma with p53 mutations and microsatellite instability. Which of the following best explains the mechanism by which chronic ulcerative colitis increases this patient's cancer risk?
Answer choices
- APersistent epithelial injury and regeneration creating cycles of oxidative stress and accumulation of somatic mutationsCorrect answer
- BIntegration of human papillomavirus (HPV) into colonic epithelial cells leading to inactivation of p53 and Rb
- CInherited germline mutations in mismatch repair genes consistent with Lynch syndrome
- DConstitutive activation of KRAS through a t(9;22) translocation event
- EDefective BRCA1-mediated homologous recombination repair
- FLoss of adenomatous polyposis coli (APC) function as the initiating somatic mutation
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