Primary gastric mantle zone lymphoma. A report of two cases.

We report two cases of primary gastric mantle zone lymphoma. Histologic examination revealed numerous lymphoid vague nodules in the mucosa and submucosa of the resected stomach. The neoplastic cells in these nodules were slightly larger than small lymphocytes and had more or less cleaved nuclei. Immunostaining on paraffin-embedded sections showed that the neoplastic cells in the nodules of these cases were LN-1- and LN-2+ and had monotypic immunoglobulin (IgM-lambda and IgM-kappa, respectively). Immunostaining on frozen tissue specimens showed that the neoplastic cells or nodules were positive for surface IgM, surface IgD, alkaline phosphatase, and DRC-1. One third to two thirds of the cells were Leu-1+ (CD5+). These results indicated that these cases were primary gastric mantle zone lymphoma. More attention should be paid to primary gastric mantle zone lymphoma because this disease might be erroneously diagnosed as either pseudolymphoma or reactive lymphoid hyperplasia of the stomach.