Primary B cell gastric lymphoma. A genotypic analysis.

A series of cases of gastric lymphoproliferative disease exhibiting the features of pseudolymphoma, frank lymphoma, or both was investigated immunohistochemically and genotypically for evidence of B cell clonality. Immunoperoxidase studies on frozen and paraffin sections showed that all cases clearly exhibited immunoglobulin light chain restriction (eight cases kappa, six cases lambda). Southern blotting using JH, Ck, and Cl probes to detect clonally rearranged gene fragments confirmed monoclonality in each case, and the immunohistochemical and genotypic data were in agreement in all cases except one (1 light chain restriction/k gene rearrangement). The study confirmed that light chain restriction in gastric lymphoid infiltrates is synonymous with monoclonality ant there is a histologic continuum between low grade B cell gastric lymphoma with features of pseudolymphoma and high grade B cell lymphoma. The authors believe that histologic and immunohistochemical features such as light chain restriction clearly discriminate reactive and neoplastic gastric lymphoid infiltration. Therefore, light chain-restricted lymphoid proliferation, previously termed pseudolymphoma is, in fact, an early stage of frank lymphoma, which obviates the need to use the term pseudolymphoma.