Gastric adenocarcinoma with choriocarcinomatous and hepatoid differentiation

ABSTRACT We report a patient with gastric adenocarcinoma with choriocarcinomatous and hepatoid differentiation. A 67‐year‐old man visited our hospital for further evaluations due to gastric adenocarcinoma. The gastric cancer was located in the prepyloric area and appeared to be a protruding mass with an infiltrative growth pattern. Initial pancreatic and postoperative hepatic and pulmonary metastases were detected radiologically. Microscopically, choriocarcinomatous and hepatoid differentiation was observed with a moderately differentiated adenocarcinoma. The choriocarcinomatous components were positive for β‐hCG and the hepatoid components were positive for α‐fetoprotein (AFP). These uncommon pathological patterns are supposed to arise from the retrodifferentiation pathway of primary gastric adenocarcinoma. The preoperative laboratory data revealed elevated serum AFP (773.4 ng/mL) and carcinoembryonic antigen (62.2 ng/mL), whereas other tests were unremarkable. The prognosis of gastric adenocarcinoma with choriocarcinomatous and hepatoid differentiation is very poor; our patient died 4 months after the operation.