Colorectal xanthomas with polypoid lesion: report of 25 cases.

Little attention has been paid to colorectal xanthoma. To clarify the clinical and pathological features of colorectal xanthoma, we report 28 colorectal xanthomas biopsied from 25 patients. All were composed of typical xanthoma cells and showed polypoid configuration. Median age of the patients was 64 years and there were 15 men and 10 women. Diabetes mellitus, constipation, and hyperlipidemia were found in two, one, and seven patients, respectively. Seventeen (60.7%) of the 28 polyps were located in the sigmoid colon and the remaining 11 in the rectum. Twenty-three polyps (82.1%) were sessile. Twelve (60.0%) of twenty polyps that were recorded were reddish in color. Only two polyps revealed a yellowish tone. Microscopically, foamy cells were present in the lamina propria, but the submucosa did not contain foamy cells. Immunohistochemically, the foamy cells invariably expressed extensive positivity for CD68. The colonic glands showed a deformity in the case with moderate to intense density of the foamy cells. The surface epithelium showed a hyperplastic change in 22 (78.6%) xanthomas. The colonic glands in four xanthomas were also associated with hyperplastic changes. The basement membrane of the surface epithelium was often thickened. Cell debris and proliferation of the capillaries were observed just below the surface epithelium in 19 (67.9%) and 22 (78.6%) xanthomas, respectively. Previous mucosal minute injury was suggested as the pathogenesis of colorectal xanthomas. Colorectal xanthomas were not identical to gastric and esophageal xanthoma, endoscopically or microscopically. We prefer the term "xanthomatous polyp" rather than xanthoma in the colorectal region. They may be regarded as a novel type of colorectal non-neoplastic polyp.