Castleman's Disease : Hyaline-Vascular Type
The follicles show abnormal germinal centers with marked vascular proliferation and hyalinization. The center of the follicle is usually depleted of lymphocytes and shows follicular dendritic cells. The follicle is surrounded by a broad mantle zone consisting of a concentric layering of lymphocytes resulting in an onion-skin appearance. The follicles are frequently penetrated radially by a sclerotic blood vessel.