Pathohistological and immunohistochemical studies on Castleman's disease of the lymph node.

Histological and immunohistochemical examinations were carried out on lymph nodes in 9 cases with Castleman's disease. In all cases, there were whorled follicle centers and proliferation of blood vessels. These findings were also considered to be important criteria for diagnosis of the plasma cell type of this disease. The whorled follicle centers often consisted of smaller concentrical structures and contained factor VIII-positive cells. In some cases, there were many small whorled structures surrounding postcapillary venules within the interfollicular areas of lymph nodes. These structures had factor VIII-positive granules indicating their endothelial origin. In 2 cases of the plasma cell type, monoclonal plasma cell proliferation (IgA, lambda and IgG, lambda, respectively) and cellular atypia were identified. These findings showed that extramedullary plasmacytoma could occur not only in the multicentric form, but also in the solitary form of Castleman's disease. In the lymph node of a case of the hyaline-vascular type, there were scattered tumour nodules consisting mainly of factor VIII-positive, atypical spindle cells suggesting associated Kaposi's sarcoma. It is conceivable that an abnormal immune state plays a role in pathogenesis of Castleman's disease.