MEDizzy - An epidemiologic study investigates the potential

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Neoplastic Disorders

An epidemiologic study investigates the potential morphologic and molecular alterations that may contribute to the development of cancers in a population. Data analyzed from resected colonic lesions show changes that suggest the evolution of a sporadic colonic adenoma into an invasive carcinoma. Which of the following best describes the mechanism producing these changes leading to colonic malignancies?

ExplanationDevelopment of colonic adenocarcinoma typically takes years, during which time multiple mutations occur within the mucosa, including mutations involving such genes as APC (adenomatous polyposis coli), K-RAS, and p53. The accumulation of mutations, rather than their occurrence in a specific order, is most important in the development of a carcinoma. Activation of proto-oncogenes, extensive regeneration, faulty TP53 genes, and amplification of growth factor receptor genes all contribute to the development of malignancies, but they are not sufficient by themselves alone to produce a carcinoma from an adenoma of the colon. Inherited loss of wild-type TP53 contributes to multiple cancers, but not to sporadic adenomas.