Chronic diarrhoea

A 56-year-old man with a history of chronic diarrhoea presented for diagnostic colonoscopy, where he was found to have a rectal subepithelial nodule. He was subsequently referred to a tertiary medical centre for further evaluation with rectal endoscopic ultrasound. Endoscopically, the nodule was hypoechoic, 2 to 3 mm in size, located in the submucosa, and did not appear to invade the muscularis propria. An uncomplicated endoscopic submucosal resection was subsequently performed. Microscopically, the nodule showed a multi-cystic complex lesion located in the submucosa, lined by ciliated pseudostratified columnar epithelium and surrounded by thin to moderately thick smooth muscle bundles and multiple lobules of seromucinous glands. There was associated acute and chronic inflammation. The rectum overlying the subepithelial lesion was lined by congested and oedematous colonic mucosa and demonstrated no connection with the underlying cystic lesion. Immunohistochemical stains showed positive p63 basal cell staining in the respiratory epithelium of the lesion, while CDX2, TTF-1, and oestrogen receptors were all negative.