(in McClain et al). Histopathology and selected immunophenotypic features of major subtypes of Castleman disease.

Hyaline vascular Castleman disease. (A) There are large follicles with wide mantle zones with focally concentric rings of small lymphocytes and regressively transformed germinal centers. The interfollicular region shows vascular proliferation and foci of plasmacytoid dendritic cells (arrow). (B) A CD123 immunostain highlights the plasmacytoid dendritic cells.

Plasma cell Castleman disease (C) In contrast to the above, the follicles appear more hyperplastic and there are sheets of plasma cells in some interfollicular regions (inset).

Multicentric Castleman disease (D) This lymph node biopsy is similar to the plasma cell type of Castleman disease; however, note the intact dilated sinus.

Multicentric Castleman disease, plasmablastic type (E) Note the follicle with a mantle zone that appears somewhat disrupted. There are foci of numerous polyclonal plasma cells (in lower portion of image). (F) Large plasmablasts (immunoblasts) with prominent nucleoli are seen in and around the mantle. (G) The plasmablasts show nuclear positivity with the immunostain for HHV8 latent nuclear antigen.