Solitary bone plasmacytomas need to flow

In this issue of Blood, 2 studies, one by Paiva et al (for the Spanish Myeloma Study group) and one by Hill et al (for the Leeds group [UK]), showed independently that flow cytometry of the bone marrow could identify patients with solitary plasmacytomas (SPs) at high risk for progression to active multiple myeloma (MM).(1,2) In the first study, 71% of patients with solitary bone plasmacytoma (SBP) who had positive flow cytometry for bone marrow phenotypically aberrant clonal plasma cells progressed to MM at a median time of 26 months, whereas only 6% of patients with negative flow cytometry progressed to myeloma (panel A). The respective values for solitary soft tissue plasmacytomas, outside of the bone, were 20% vs 6%, respectively.(1) In the second study, the results were similar: 72% of patients with SBP and occult bone marrow disease detected by flow cytometry vs 12.5% without clonal plasma cells in the bone marrow also progressed to MM at a median time of 26 months (panel B).(2) These findings are of great importance because multiparameter flow cytometry may be included in the initial work-up of a patient with a suspected SP.