INTRODUCTION
Castleman disease (CD, angiofollicular lymph node hyperplasia) describes a heterogeneous group of lymphoproliferative disorders that share common histopathologic features.CD is classified into at least three distinct disorders based on the number of regions of enlarged lymph nodes with characteristic histopathologic features and the presence/absence of human herpesvirus 8 (HHV-8, also called Kaposi sarcoma associated herpesvirus [KSHV]) infection:
●Unicentric CD (UCD) involves one or more enlarged lymph node(s) in a single region of the body that demonstrates CD histopathologic features that lie along a spectrum with hyaline vascular histopathologic subtype on one end, plasmacytic histopathologic subtype on the other, and a "mixed" subtype in the middle. A subset of patients have systemic symptoms.
●Multicentric CD (MCD) involves multiple regions of lymphadenopathy that demonstrate CD histopathologic features that lie along a spectrum with hypervascular histopathologic subtype on one end, plasmacytic histopathologic subtype on the other, and a "mixed" subtype in the middle. These patients also have systemic inflammatory symptoms with generalized lymphadenopathy, hepatosplenomegaly, cytopenias, and organ dysfunction due to excessive pro-inflammatory hypercytokinemia, often including interleukin (IL)-6. MCD is further subclassified according to the presence of HHV-8:
•HHV-8-associated MCD – Approximately half of MCD cases are caused by HHV-8 infection in human immunodeficiency virus (HIV)-positive or otherwise immunocompromised individuals, and these cases are referred to as HHV-8-associated MCD.