Gastric Adenocarcinoma With Enteroblastic Differentiation and Coexisting Well-Differentiated Tubular Adenocarcinoma: A Case Report

A 92-year-old male was referred to our hospital owing to progressive anemia and a positive fecal occult blood test. Upper gastrointestinal endoscopy revealed an advanced gastric carcinoma on the posterior wall of the lower gastric body, which was diagnosed as tubular adenocarcinoma by biopsy. The patient underwent an open distal gastrectomy, and the operative specimen showed a 45-mm-sized type 3 lesion on the posterior wall of the lower gastric body and a 35-mm-sized type 0-IIa tumor on the oral side of the type 3 lesion. Histopathological examination revealed that the type 3 lesion contained cells with pale sporangia, and immunohistochemistry was positive for SALL4, α-fetoprotein, and Glypican-3, leading to a diagnosis of gastric adenocarcinoma with enteroblastic differentiation (GACED). The type 0-IIa tumor was negative for these immunostainings and was identified as a well-differentiated tubular adenocarcinoma. There was no mixture of the two tumors except for the border area. Intraoperative peritoneal washing cytology was positive, and the stage was pStage IV. Owing to his advanced age, postoperative chemotherapy was not initiated. At three months postoperatively, lung and liver metastases were detected. We report a case of GACED with coexisting well-differentiated tubular adenocarcinoma.