A case of CA19‐9‐producing adenocarcinoma of the remnant stomach resembling gastritis cystica polyposa

Gastritis cystica polyposa (GCP) is a well-known precancerous lesion of the remnant stomach. We report a case of carbohydrate antigen (CA) 19–9-producing well-differentiated adenocarcinoma of the remnant stomach that resembled GCP. The patient was a 66-year-old Japanese man who had undergone subtotal gastrectomy 20 years previously. The tumor developed in the remnant stomach at the anastomotic line. Histologically, the lesion completely encircled the gastroenterostomy stoma. There was florid growth of glands with cystic dilatation and minimal atypia extending through the thickened muscularis propria into the subserosa. Small foci of less well-differentiated adenocarcinoma were also detected, including irregular glands or small clusters of mucus-producing cells with moderate atypia. Immunostaining revealed that numerous tumor cells were positive for carcinoembryonic antigen and CA19-9, whereas only a few cells were positive for p53. The macroscopic, histopathological and immunohistochemical findings indicated a diagnosis of CA19-9-producing well-differentiated adenocarcinoma of the remnant stomach. To avoid underdiagnosis, careful attention should be paid to the above-mentioned morphological features and immunohistochemical findings, in addition to the endoscopic findings.