Angiofollicular lymph node hyperplasia (Castleman's disease): an immunohistochemical and enzyme-histochemical study of the hyaline-vascular form of lesion.

Tissues from five cases of angiofollicular lymph node hyperplasia have been studied. All had the histological structure of the hyaline-vascular type of lesion; large numbers of very compact lymphoid follicles were distributed evenly throughout a highly vascular tissue. The follicles were characterized by their small size, a vascular poorly cellular and frequently hyalinized centre, and a 'tight' concentric mantle of small lymphocytes arranged in layers producing an 'onion-skin' appearance. The interfollicular tissue was characterized by the large numbers of small vessels mainly hyalinized capillaries and a few high endothelial venules and the presence of variable numbers of lymphocytes, plasma cells, immunocytes and immunoblasts. The immunoperoxidase method demonstrated polytypic cytoplasmic immunoglobulin in the small numbers of centroblasts and plasma cells within the follicle centres and in the plasma cells and immunocytes in the interfollicular tissue. Large numbers of suppressor T cells were present in the interfollicular areas and only scattered helper T cells were seen within the lymphocyte mantles. A strong reaction for factor VIII-related antigen was seen in the endothelium of the interfollicular high endothelial venules but only a weak reaction in the vessels in the follicle centres. A concentric distribution pattern of the dendritic reticulum cells was seen with the metalophil impregnation method of Marshall and with the enzyme histochemical methods for acid alpha-naphthyl acetate esterase and 5'-nucleotidase. This pattern differs from the zonal distribution of these cells seen in reactive lymphoid follicles. The nature and possible pathogenesis of AFLNH are discussed and contrasted with reactive hyperplasia.