Castleman disease is a group of uncommon lymphoproliferative disorders characterized by lymph node enlargement, characteristic features on microscopic analysis of enlarged lymph node tissue, and a range of symptoms and clinical findings. Research on Castleman disease is rapidly evolving and the disease is becoming better understood. Castleman disease is named after Benjamin Castleman, who first described the disease in 1956. The Castleman Disease Collaborative Network is the largest organization focused on the disease and is involved in research, awareness, and patient support.