Representative examples of UCD. HV subtype is characterized by the presence of regressed atretic germinal centers. There is increased vascularity with hyalinization, prominence of often dysplastic FDCs, and expanded mantle zones in an onion-skin appearance. There are radially penetrating blood vessels causing a lollipop appearance, multiple germinal centers within the same mantle zone referred to as twinning or budding, tight aggregates of plasmacytoid dendritic cells, and architectural disruption with obliterated sinuses. PC subtype exhibits hyperplastic germinal centers and profuse plasmacytosis. Mixed subtype exhibits a combination of HV and PC features.