Morphologic features of cases of UCD and MCD with genetic abnormalities. (A-B) Case 3, HHV8⁻/iMCD with plasmacytic histology. At low-power magnification, regressed follicles are seen with onion skinning of mantle zones and “twinning” of follicles; increased plasma cells are clearly seen in interfollicular regions with mild vascularity. (C-D) Case 5, UCD-MV. At low-power magnification, regressed follicles are seen with onion skinning of mantle zones along with increased vascularity in interfollicular regions. At high-power magnification, increased plasma cells are clearly seen along with increased vascularity. (E-F) Case 14, UCD-HVV. At low-power magnification, regressed follicles are seen with prominent onion skinning of mantle zones and “twinning” of follicles. At high-power magnification, increased vascularity is present without increased plasma cells. In all panels, images on cases are taken in sequence at ×100 (left) and ×400 (right) magnification; all images are from hematoxylin and eosin–stained slides.