Immunohistochemical labeling patterns illustrating the 3 PCNSL immunoprofiles. (A) GCB: CD10⁺BCL-6⁺MUM1^-CD138^-. (B,C) The 2 predominant ABC patterns, respectively: activated GCB-cell CD10^-BCL-6⁺MUM1⁺CD138^- and non–GCB-cell CD10^-BCL-6^-MUM1⁺CD138^-. Images were observed using a LEITZ DMR microscope (Leica, Wetzlar, Germany) with a 20 ×/0.70 numeric aperture objective, operating with a 3CCD color video camera (DXC.93OP; Sony, Tokyo, Japan). Image acquisition was performed using Analysis software (SIS Soft Imaging Software, Reutlingen, Germany).