Gastric parietal cell carcinoma with an unusual, lymphoma-like histologic appearance: report of a case.

We report a case of gastric carcinoma with an unusual histologic appearance and type of cellular differentiation. The tumor was resected from an 85-yr-old man who presented with epigastric pain and monoclonal gammopathy. The tumor was antral in location and transmurally infiltrated the stomach wall. Histologically, the tumor closely resembled a lymphoma with diffuse poorly cohesive sheets of tumor cells interspersed with histiocytes. Immunohistochemical study, however, clearly demonstrated the epithelial nature of this tumor. Electron microscopy also revealed evidence of epithelial differentiation and features of parietal cell differentiation. In this report, we describe the light and electron microscopic findings, immunohistochemical staining properties, and DNA flow cytometric findings of this tumor and briefly review the literature on parietal cell carcinomas.