A Man with Back Pain and Weakness

He had a prior history of mediastinal lymphadenopathy with nondiagnostic biopsies. Current examination showed lymphadenopathy of the axilla/arm and violaceous macules (see Figure 1). He also had severe microcytic anemia, markedly elevated inflammatory markers, and hypergammaglobulinemia. CT imaging confirmed widespread lymphadenopathy with hepatosplenomegaly. A lymph-node core needle biopsy was inconsistent with lymphoma, but excisional biopsy revealed germinal centers containing polyclonal plasma cells penetrated by blood vessels (“lollipop sign”), consistent with multicentric Castleman’s disease.