Contributed by Xin Li, MD and Katrina Han, MD
A 58 year old woman with a history of chronic diarrhea, post-menopausal uterine bleeding, and depression underwent a routine colonoscopy for colon cancer screening which demonstrated a large, nearly obstructing mass extending from the proximal rectum into the distal sigmoid colon. The colonoscopy examination shows a large mass partially occluding lumen of rectosigmoid colon (Fig. 1). The colonoscope could be traversed proximally and the remainder of the examination was normal.
A 13.0 x 7.0 x 4.0 cm tan-brown polypoid multinodular lesion is located on the mucosal surface of the colon. The cut surface of the lesion is tan-pink and slightly gelatinous with focal cystic areas (Fig. 2).
Histological sections demonstrate that cystically dilated glands scatter beneath the colonic mucosa and show focal crowding. High power view reveals benign-appearing endometriotic glands and stroma, without atypia. Some glands show mucinous metaplasia (Fig. 3).
The glands are positive for CK7, ER, PAX8 and Vimentin; negative for CK20 and monoclonal CEA (Fig. 4).