Colitis cystica profunda indefinite for dysplasia in Crohn disease: a potential diagnostic pitfall

Colitis cystica profunda (CCP) is a nonneoplastic condition characterized by misplaced glands deep to the muscularis mucosae of the colon and may be difficult to differentiate from well-differentiated mucinous adenocarcinoma. Absence of dysplasia in CCP usually aids in this distinction. We present a challenging case of CCP in the setting of Crohn disease (CD) containing foci of atypical epithelium. A right hemicolectomy from a 46-year-old woman contained a stricture associated with a proximal multilocular cystic lesion containing mucin-filled glands dissecting through the colonic wall. These glands had lobulated architecture with smooth contours surrounded by lamina propria and lacking desmoplastic stroma. The epithelium had focal nuclear crowding, enlargement, and hyperchromasia, with increased nucleus to cytoplasm ratio, but overall preserved polarity. Atypical cells were focally positive for CK7 and p53, with increased MIB-1 staining. These findings were interpreted as indefinite for dysplasia. Chronic transmural inflammation and mucosal regeneration probably facilitated epithelial misplacement, which secondarily developed cytologic atypia. However, the overall architecture and lack of dysplasia in the overlying mucosa argue against a diagnosis of adenocarcinoma. Our case illustrates the difficult diagnosis of this uncommon but problematic phenomenon, awareness of which is paramount for pathologists and clinicians participating in the management of CD patients.