Here are multiple adenomatous polyps of the cecum. A small portion of terminal ileum appears at the right. This is a patient with hereditary non-polyposis colon carcinoma (HNPCC) syndrome. Compared to adenomatous polyposis coli (APC), in HNPCC there are fewer polyps and an older age for development of carcinoma. The defect in HNPCC is the inheritance, in an autosomal dominant fashion, of a faulty DNA mismatch repair gene, and most HNPCC tumors demonstrate microsatellite instability (variations in dinucleotide repeat sequences).

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