Giant lymph node hyperplasia. An immunopathologic and ultrastructural study of a case of the multicentric plasma cell variant.

A case of the multicentric plasma cell variant of giant lymph node hyperplasia (Castleman's disease) was studied. The left supraclavicular and axillary lymph nodes were affected. The parafollicular region of the lymph nodes was greatly expanded by sheets of mature plasma cells and by regionally concentrated as well as singly occurring immunoblasts. Both plasma cells and immunoblasts were polyclonal, as judged by the heterogeneity of immunoglobulin light-and heavy-chain components documented by immunofluorescence microscopy and immunohistochemistry. Ultrastructurally, free ribosomes and polyribosomes were the predominant cytoplasm organelles seen in immunoblasts. In plasma cells, rough endoplasmic reticulum was typically abundant and often contained electron-dense secretory product.