Case of malignant lymphoma associated with primary systemic plasmacytosis with polyclonal hypergammaglobulinemia.

Systemic plasmacytosis (SP), which has a histologic appearance similar to that of multicentric Castleman's disease (MCD), is also known as benign plasma cell proliferation with polyclonal hypergammaglobulinemia, cutaneous plasmacytosis, and/or generalized plasmacytic lymphadenopathy. The prognosis of SP reportedly has been good. A 59-year-old Japanese man was treated for multiple cutaneous lesions of his trunk as well as polyclonal hypergammaglobulinemia. A skin biopsy showed infiltration of lymphocytes and polyclonal plasma cells in the dermis. The patient developed enlarged superficial lymph nodes 5 years later, and T-cell lymphoma, diffuse mixed type, was diagnosed. At that time, his cutaneous plasmacytosis remained but the polyclonal hypergammaglobulinemia had resolved. Ours is the first reported case of SP to be complicated by the development of T-cell lymphoma.