[A case of so-called plasma cell granuloma of the stomach--demonstration of monoclonal immunoglobulin (IgM, K) in the plasma cells].

A patient with a surgically removed plasma cell granuloma of the stomach is reported. The patient was a 54-year-old male, the lesion was IIc-like on the anterior wall of the antrum. Histologically conspicuous features were marked thickening of the submucosa by fibrosis, hyperplastic lymph follicles and massive infiltration of mature plasma cells. However, immunohistochemical study using the PAP technique demonstrated the monoclonal nature of the infiltrating plasma cells which were positive for IgM, k. This is the fourth case of plasma cell granuloma reported in the literature, however, our findings also suggested that this might be an early stage of plasmacytoma.