The nonlymphoid microenvironment of reactive follicles and lymphomas of follicular origin as defined by immunohistology on paraffin-embedded tissues.

Twenty-five reactive lymph nodes, 10 palatine tonsils, and 72 B-cell non-Hodgkin's lymphomas (NHLs) of supposed follicular origin were investigated in an immunohistologic study of fixed, paraffin-embedded tissues using a panel of monoclonal antibodies reactive with antigens resistant against fixation and paraffin-embedding techniques together with polyclonal antibodies. The results concerning the microenvironmental organization of reactive lymphoid follicles confirmed that the distribution of CD21+ and CD23+ dendritic reticulum cells, vimentin+ fibroblastic reticulum cells, and CD68+ tingible-body macrophages is heterogeneous with reference to their immunostaining patterns and topographic localization within the germinal center and mantle zone. Moreover, a close microenvironmental similarity between the follicular lymphomas of supposed germinal center or mantle zone origin and their normal counterparts was noted. The study of the microenvironment of the B-zone small lymphocytic lymphoma cases, showing the same distribution patterns for the nonlymphoid cells as seen in mantle zone lymphomas, corroborated the supposed follicular origin of this unusual variant of small lymphocytic lymphoma. In conclusion, this study shows that monoclonal antibodies recognizing CD21, CD23, and CD68 antigens may be valuable additions to vimentin, S-100 protein, laminin, and type IV collagen antibodies for investigating the microenvironmental organization of lymphoid tissues in both normal and neoplastic conditions.