Hypervascular: similar to hyaline vascular features, but seen in iMCD rather than UCD. Includes regressed germinal centers, follicular dendritic cell prominence, hypervascularity in interfollicular regions, and prominent mantle zones with an "onion-skin" appearance. Mixed: presence of a combination of hyaline vascular/hypervascular and plasmacytic features in the same lymph node.UCD most commonly demonstrates hyaline vascular features, but plasmacytic features or a mix of features may also be seen. iMCD more commonly demonstrates plasmacytic features, but hypervascular features or a mix of features are also seen. All cases of HHV-8-associated MCD are thought to demonstrate plasmablastic features—similar to plasmacytic features, but with plasmablasts present. The clinical utility of subtyping Castleman disease by histologic features is uncertain, as histologic subtypes do not consistently predict disease severity or treatment response. Guidelines recommend against using histologic subtype to guide treatment decisions. Staining with latency-associated nuclear antigen (LANA-1), a marker for HHV-8 infection, should be measured in all forms of Castleman disease but is positive only in HHV-8-associated MCD.Diseases other than Castleman disease can present with similar histologic findings in lymph node tissue, including:
Infectious causes: Epstein-Barr virus, human immunodeficiency virus, tuberculosis
Autoimmune diseases: Systemic lupus erythematosus, rheumatoid arthritis
Lymphoproliferative disorders: lymphoma, autoimmune lymphoproliferative syndrome

History
Unicentric Castleman disease was first described in a case series by Benjamin Castleman in 1956. By 1984, a number of case reports had been published describing a multicentric variant of the disease and with some reports describing an association with Kaposis sarcoma. In 1995, the association between HHV-8 and Castleman disease was described in patients with HIV.
Castleman disease (CD) describes a group of rare lymphoproliferative disorders that involve enlarged lymph nodes, and a broad range of inflammatory symptoms and laboratory abnormalities. Whether Castleman disease should be considered an autoimmune disease, cancer, or infectious disease is currently unknown. Castleman disease includes at least three distinct subtypes: unicentric Castleman disease (UCD), human herpesvirus 8 associated multicentric Castleman disease (HHV-8-associated MCD), and idiopathic multicentric Castleman disease (iMCD). These are differentiated by the number and location of affected lymph nodes and the presence of human herpesvirus 8, a known causative agent in a portion of cases. Correctly classifying the Castleman disease subtype is important, as the three subtypes vary significantly in symptoms, clinical findings, disease mechanism, treatment approach, and prognosis. All forms involve overproduction of cytokines and other inflammatory proteins by the bodys immune system as well as characteristic abnormal lymph node features that can be observed under the microscope. In the United States, approximately 4,300 to 5,200 new cases are diagnosed each year.Castleman disease is named after Benjamin Castleman, who first described the disease in 1956. The Castleman Disease Collaborative Network is the largest organization dedicated to accelerating research and treatment for Castleman disease as well as improving patient care. Classification
Castleman disease (CD) can involve one or more enlarged lymph nodes  in a single region of the body (unicentric CD, UCD) or it can involve multiple enlarged lymph node regions (multi centric CD, MCD).