Monoclonality and polyclonality of plasma cells in Castleman's disease of the plasma cell variant.

Castleman's disease of the plasma cell variant observed in 21 patients was investigated morphologically and by immunohistochemistry. The male to female ratio was 2.5:1. The age ranged from 18 to 71 years (mean age 47.6 years). Histologically, the lesions were characterized by numerous, evenly distributed germinal centres ranging from large hyperplastic to small hyaline-vascular types with moderate to extensive sheets of plasma cells in between. In all cases with generalized lymph node enlargement dilated sinuses could be found. Immunohistochemical studies demonstrated a polyclonal plasma cell population in 11 of 18 lesions. Seven lesions contained a monoclonal plasma cell population, five with IgG/lambda and two with IgA/lambda; clinically, two of these patients had generalized lymphadenopathy; in none could manifestation of a plasmacytoma be found outside the lymph node lesion; only two of the seven patients exhibited a paraproteinaemia (IgG/lambda and IgA/lambda, respectively) corresponding to the Ig type of the proliferated plasma cells. Six patients with polyclonal lesions had constitutional symptoms such as fever, anaemia, polyclonal hypergammaglobulinaemia; one of these six patients manifested symptoms consistent with a diagnosis of Takatsuki syndrome. The monoclonal plasma cell type of Castleman's disease did not progress to a generalized disease. This monoclonal variant may be a lymph nodebased type of benign monoclonal gammopathy.