CD81 and monoclonal gammopathy: In this study, we show that a) our single-tube 10-color MFC panel was reliable for MRD detection in the whole spectrum of monoclonal gammopathies (MGUS, SMM, and MM) with a consistently high sensitivity, b) the additional markers included in this panel, prominently CD81 and CD200, were valuable and informative for MRD detection, while in select cases kappa/lambda proved beneficial, and c) MRD assessment was possible in apheresis samples likewise to BM, with MRD apheresis status holding predictive value for responses after ASCT.