CD histopathology. (A-B) HV histopathology. (A) Low power (hematoxylin and eosin stain; original magnification ×20) and (B) high power (hematoxylin and eosin stain; original magnification ×100). Most commonly seen in UCD, these lymph nodes are often characterized by capsular fibrosis with broad fibrous bands traversing through the lymph node; an increased number of lymphoid follicles are scattered throughout the cortex and medulla with often >1 germinal center sharing the same mantle zone. Mantle zones are broad and composed of concentric rings of small lymphoid cells (“onion skin pattern”). Germinal centers are often depleted of B cells and are predominantly composed of follicular dendritic cells with prominent hyaline deposits. Sclerotic blood vessels penetrating within the germinal centers forming so-called “lollipop lesions” are observed. Follicular dendritic cells can show dysplastic features. The interfollicular region is composed of prominent high endothelial venules with plump endothelial cells, often surrounded by clusters of plasmacytoid dendritic cells and stromal proliferation. PCs, immunoblasts, and eosinophils are also part of the interfollicular infiltrate, but sheets of PCs are not seen. (C-D) PC histopathology. (C) Low power (hematoxylin and eosin stain; original magnification ×20) and (D) high power (hematoxylin and eosin stain; original magnification ×100). Lymph nodes demonstrating PC histopathology are distinguished by the presence of sheets of PCs in the interfollicular zone. The interfollicular region can also contain prominent high endothelial venules. Some eosinophils and mast cells may also be present. There is follicular/germinal center hyperplasia with sharply defined mantle zones and polarized germinal centers, with frequent mitosis and histiocytes with nuclear debris.