Gastric-type extremely well-differentiated adenocarcinoma arising in the blind pouch of a bypassed stomach, presenting as colonic pseudo-obstruction.

Gastric carcinoma after gastric bypass is rare. Extremely well-differentiated adenocarcinoma (EWDA) of the stomach is a rare variant that has been mostly reported in Japan. We present a case of a 68-year-old man with EWDA arising in the bypassed stomach that presented as a colonic pseudo-obstruction (CPO). Several imaging, endoscopic and pathologic studies performed in the course of 2 months were non-diagnostic. An iatrogenic duodenal perforation during a diagnostic procedure led to an emergent exploratory laparotomy in which the dilated colonic segment was resected. Pathologic examination showed metastatic EWDA in the colonic wall. Post-operative complications led to the patient's demise. At autopsy the primary tumor was identified in the blind pouch of the bypassed stomach. A literature review on gastric EWDA and carcinomas arising in bypassed stomachs is discussed. EWDA of the stomach is rare, difficult to diagnose, and shows an aggressive clinical course discordant with its near-benign histology. Gastric cancer arising in a bypassed stomach is uncommon; when it occurs it is usually diagnosed at advanced stage. Surveillance of the blind pouch is not currently recommended. Malignant infiltration of the colonic wall should be included in the differential diagnosis of CPO of unclear etiology.