Immunoblastic lymphoma with extracellular and intravascular immunoglobulin deposits: immunocytochemical and electron microscopic studies.

Immunoblastic lymphoma (IBL) showing features of angioimmunoblastic lymphadenopathy (AIBL) is described. Abundant eosinophilic extracellular deposits were present in lymph nodes. Electron microscopic and immunoperoxidase studies showed this material was composed of degenerating tumor cells and polyclonal immunoglobulins (Mu and Alpha heavy chains and Kappa and Lambda light chains). Numerous arborizing vessels were thickened with monoclonal IgM(K) immunoglobulins. The tumor cell lysis and degeneration are though to be due to the high cell turnover and immune reaction to unrecognized substances.