Adenocarcinoma in solitary large hyperplastic polyp diagnosed by magnifying colonoscope: report of a case.

We report a case of carcinoma in a hyperplastic polyp in a 78-year-old female that was diagnosed before resection using a magnifying colonoscope. The patient presented with fecal occult blood and underwent total colonoscopy, which revealed a 12-mm sessile polyp in the cecum. When seen in magnified view, an irregularly shaped pit was evident at the center of the polyp that was distinct from the asteroid-type pits observed over most of the lesion. We diagnosed this lesion as a hyperplastic polyp with a carcinoma component. The patient underwent endoscopic mucosal resection, and histologic section revealed a well-differentiated intramucosal adenocarcinoma in the hyperplastic polyp. Hyperplastic polyps of the colon are regarded as benign, nonneoplastic lesions. Few have reported carcinomas in or with hyperplastic polyps, and most of those were diagnosed after resection and histologic investigation. The literature suggests a precise observation and consideration of resection for large solitary hyperplastic polyps in the right side of the colon, because the risk of malignancy is high. Magnifying colonoscopy is helpful for observing the surface in detail and for correctly diagnosing and managing the lesion.