Lymph nodes are enlarged with follicular hyperplasia and relative preservation of lymph node architecture.
The process evolves through various stages which affect the histologic appearance.
Germinal centers are numerous and often poorly defined. They may range in size from small to large. They may contain a relative increase in large, pale, eosinophilic cells may be either histiocytes or follicular dendritic cells.
Vascularity in the germinal centers is often increased. In the hyaline-vascular variant the vessels show hyaline walls.
Concentric layers of lymphocytes may surround the germinal centers ("onion-skinning"). This may be prominent or obscured.
The interfollicular space may show:
(1) dilated sinuses
(2) increased plasma cells, which may occur in sheets with atypical forms in the plasmablastic variant
Herpesvirus-8 (Kaposi sarcoma-associated herpesvirus) can be demonstrated in most cases (almost all if HIV-associated).
