CD274 and myeloid sarcoma: Careful cell counts performed on about 80 serial sections from eight tissue blocks of six MS cases, subjected to single- and double-immunostainings, revealed that more than 60% of PD-L1+ cells co-expressed the latency EBV antigens EBNA2 and LMP2A in the inflamed meninges (49 ± 5% and 15 ± 3%, respectively).