Some groups described a significant increase of PD-L1 expression on plasmacells (PC) from MM patients (including both newly diagnosed and relapsed myeloma) as compared with monoclonal gammopathies of undetermined significance (MGUS) and healthy donors (HDs) (7, 11, 12), while others did not find any significant difference (13, 15). This evidence concerns the gene CD274 and monoclonal gammopathy.