This issue of Hematology/Oncology Clinics, edited by Dr. Frits van Rhee and Dr. Nikhil C. Munshi, focuses on Castleman's Disease. Topics include, but are not limited to, Epidemiology; Pathogenesis; Role of Interleukin 6 in Castleman Disease; Pathology, Diagnosis; Unicentric Castleman Disease; Treatment of HHV8 related Multicentric Castleman Disease; Treatment of HHV8 negative Castleman Disease; TAFRO Syndrome; POEMS; and more.