Polymorphic reticulosis: a malignant lymphoma of B-cell lineage.

Whether the pathogenesis of polymorphic reticulosis is from T cells, B cells, or histiocytes has been controversial. In this study, the Southern blot hybridization technique was used to analyze immunoglobulin and T-cell receptor beta-chain genes and to perform the conventional surface marker analysis in two patients with polymorphic reticulosis. The immunophenotype demonstrated the presence of predominantly mature, activated T-lymphocytes, minimal B-cells, and no natural killer cells or monocytes/granulocytes. The mature T-cell phenotype could be due to either inflammatory infiltrates or neoplastic cells of peripheral T-cell type, because the two coexist in polymorphic reticulosis tumors. The value of surface marker examination is limited in the analysis of PMR tumors. However, genetic analysis revealed that only Ig genes were rearranged, with no rearrangement of the TCR beta gene. Rearrangement of immunoglobulin genes occurs in B-lineage lymphoid neoplasms and is thought to be a criterion for diagnosis of lymphoid neoplasms. Based on genetic analysis and clinicopathologic information, this study concluded that polymorphic reticulosis is a malignant lymphoma of B-cell lineage.