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156408 Pathology

A 26-year-old man with a family history of colon carcinoma undergoes a surveillance colonoscopy. It reveals hundreds of polyps in the colon and two focal 0.5-cm ulcerated areas. A biopsy specimen from an ulcer reveals irregularly shaped glands that have penetrated into the muscular layer. Which of the following molecular events is believed to occur very early in the evolution of his colonic disease process?

AActivation of the WNT signaling pathway
BInability to hydrolyze GTP-bound RAS
CLoss of heterozygosity affecting the p53 gene
DMutations in mismatch repair genes.
Pathology
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