Hepatoid gastric adenocarcinoma. A histological and immunohistochemical study of a case.

A case of gastric adenocarcinoma with patterns resembling those of hepatocellular carcinoma is reported. The hepatoid component of the tumour was characterized by discrete masses, nests and broad bands of large polyhedral cells with central nuclei, prominent nucleoli, and abundant eosinophilic cytoplasm; single-nucleus giant cells were frequently noted. Varying numbers of tumour cells stained immunohistochemically for alpha-fetoprotein (AFP), alpha-1-antitrypsin (AAT), and albumin. Thus, in this hepatoid gastric adenocarcinoma tumour cells demonstrated both morphologic and immunohistochemical features of partial differentiation in hepatocellular carcinoma. Careful histological examination in conjunction with the immunohistochemical demonstration of AFP and other serum proteins can provide an useful contribution to the diagnosis of this rare histological type of gastric carcinoma.