Systemic lymphoproliferative disorder with morphologic features of Castleman's disease. Immunoperoxidase study of cytoplasmic immunoglobulins.

Lymph node biopsy specimens from nine patients with a systemic lymphoproliferative disorder morphologically resembling Castleman's disease were studied for the presence of cytoplasmic immunoglobulins. After trypsinization of tissue sections, the avidin-biotin-peroxidase method was used to stain for IgG, IgA, and IgM heavy chains and kappa and lambda light chains. All cases showed polyclonal proliferation of plasma cells. The predominant immunoglobulin class observed was IgG. The IgM-containing cells tended to be localized concentrically around germinal centers. No notable changes were seen in multiple biopsy specimens from five patients. Polyclonal staining was also observed in lymph nodes obtained at autopsy from a patient who died of a disseminated atypical immunoproliferative process. The polyclonal staining pattern in these cases confirms the reactive nature of this systemic lymphoproliferative disorder.