Immunohistochemical stains were performed on formalin-fixed, paraffin-embedded (FFPE) tissue sections following routine
procedures on a Ventana Benchmark automated stainer (Roche Ventana Medical Systems, Tucson, AZ), using the antibodies against CD20
(L26, Roche Diagnostics), CD3 (2GV6, Ventana), CD79a (SP18, Roche Diagnostics), PAX-5 (SP34, Roche Diagnostics), LMP1 (CS
1–4, Dako), EBNA2 (PE2, Abcam), (CD138 (B-838, Roche Diagnostics), kappa (rabbit, Roche Diagnostics), lambda (rabbit,
Roche Diagnostics), CD38 (SPC32, Vector), MUM-1 (MRQ-43, Roche Diagnostics), Ki-67 (MIB-1, Dako), IgG (rabbit, Dako), IgM (rabbit,
Dako), and IgA (rabbit, Dako). Epstein-Barr virus-encoded small RNA (EBER) in situ hybridization was performed as previously
described 13 (link).