Gastric pseudolymphoma with monotypic cytoplasmic immunoglobulin.

Two cases of hyperplastic lymphoid lesion of the stomach with cytoplasmic immunoglobulin of monotypic pattern are presented. Both patients were young, and the postgastrectomy course was uneventful for 38 and 76 months, respectively. The lesion had been diagnosed as pseudolymphoma based on the presence of hyperplastic follicles with germinal center and mixed infiltration of plasma cells and mature lymphocytes with no significant cytologic atypia. However, the immunoperoxidase method showed monotypic cytoplasmic immunoglobulin; lambda/IgM in one case and lambda/IgG in the other. The staining pattern of germinal centers was also monotypic in one, but polytypic in the other. These cases suggest the presence of monoclonal but reactive lymphoid hyperplasia, i.e., monoclonal-type pseudolymphoma in the stomach. On the other hand, this type of lesion has to be carefully followed for the possible development of malignant lymphoma.