Neoplastic argentaffin cells with intracytoplasmic eosinophilic granules in a gastric adenocarcinoma.

A case of poorly differentiated adenocarcinoma of the stomach with unique histological features is reported: in addition to characteristic adenocarcinoma cells, a large number of tumor cells contained bright eosinophilic and argentaffin granules in their cytoplasm. On routine histologic examination, the latter cells closely resembled the endocrine cells present in the normal human gastrointestinal tract, although the granules were distributed throughout the cytoplasm and did not show any polarity, which is usually subnuclear in normal endocrine cells. Immunohistochemical studies demonstrated positive staining for lysozyme, CEA, gastrin and HCG. Electron microscopic examination revealed cytoplasmic neurosecretory granules, and some tumor cells were found to contain both secretory granules and mucinous material within the same cytoplasm. These neoplastic endocrine cells presumably originated from primitive digestive system elements capable of differentiating towards both endocrine and mucus-secreting varieties.