Mixed epithelial polyps in association with hereditary non-polyposis colorectal cancer providing an alternative pathway of cancer histogenesis

Abstract

A member of a hereditary non-polyposis colorectal cancer (HNPCC) family developed two colorectal cancers and multiple polyps within four years of a negative colonoscopic examination. One of the cancers was only 4 mm in diameter and showed the gross and endoscopic appearances of a de novo carcinoma. Microscopic examination of multiple levels revealed a mixed hyperplastic polyp/adenoma (mixed polyp) in contiguity with the cancer. The colon harboured additional polyps of which five were tubular adenomas, seven were hyperplastic polyps and seven were mixed polyps (architecturally compatible with hyperplastjc polyps but with atypical cytology). Atypical features of the mixed polyps included tripo..