Gastric small cell carcinoma with squamous and neuroendocrine differentiation.

A rare gastric carcinoma containing diverse components, that is, neuroendocrine (small cell carcinoma), squamous and gland-like elements in an 82 yr old woman is described. Radiologic examination revealed a large ulcerated tumor, and a Borrmann type II tumor, 6.5 x 5 cm, was found in the resected stomach. Histologically, the tumor was mainly composed of small cells with hyperchromatic nuclei and scant cytoplasm. Argyrophilic granules were seen in these cells. There were also scattered foci of large cells with features of squamous cells, and many intermediate cells with oncocytic cytoplasm. The small cancer cells were positive for chromogranin A and neuron specific enolase. Squamous cell nests were positive for high molecular cytokeratin (CK), and intermediate cells were positive for low molecular CK. Electron microscopic examination revealed secretory granules in the small cells and tonofilaments in the squamous cells. This tumor might have originated from the pluripotential stem cell in the gastric epithelium.