This article ties to SDG 3. This clinical review article, published in Hematology/Oncology Clinics, presents current understanding of the pathogenesis for each subtype of CD as of 2017. Although understanding of CD has slowly improved over the last 6 decades, leading to improved patient survival and quality of life, additional research is needed. The authors anticipate significant progress to be made in the coming years through research studies led by the CDCN, including the ACCELERATE (Advancing Castleman Care with an Electronic Longitudinal registry, E-Repository, And Treatment/Effectiveness research) Natural History Registry (www.CDCN.org/ACCELERATE), which is open for patient self-enrollment.