In 11 patients a subpopulation of CD19 CD20 CD22 CD79b-positive B lymphocytes (4%; range 1–22%), with a normal/balanced Ig kappa/lambda ratio evaluated on the CD22-positive population, was identified: 5 PCNSL, 5 diffuse large B-cell lymphoma (DLBCL), 1 follicular lymphoma (Table 3) (Figures 2A–C). Here, CD22 is linked to primary central nervous system lymphoma.