This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Neoplasia, Subject name: Pathology
[{'content': 'A 50-year-old woman undergoes screening colonoscopy as part of a routine health maintenance work-up. An isolated 1-cm pedunculated polyp is found in the sigmoid colon. The excised polyp histologically shows well-differentiated glands with no invasion of the stalk. Which of the following investigational research procedures can distinguish most clearly whether the polyp represents hyperplasia of the colonic mucosa or a tubular adenoma? \nSelect and explain. \nA. Flow cytometry to quantitate cells in the S phase, B. Histochemical staining for mucin, C. Immunohistochemical staining for keratin, D. Molecular marker of clonality', 'role': 'user'}, {'content': 'Answer: D \nExplanation: A true neoplasm is a monoclonal proliferation of cells, whereas a reactive proliferation of cells is not monoclonal. Molecular genetic analysis, such as allelotype analysis with microsatellite markers, shows clonality. Reactive and neoplastic cellular proliferation may have similar histochemical and immunohistochemical staining patterns based on the type of cells and proteins that are present. Flow cytometry is effective at indicating the DNA content, aneuploidy, and growth fraction, but does not indicate clonality.', 'role': 'assistant'}]