Flow cytometric features of B-ALL-like cell populations arising during lenalidomide therapy. BM flow cytometry dot plots depicting abnormal immature B-cell populations arising during lenalidomide therapy, which ultimately resolved with holding lenalidomide. Plots reflect normal case (blue dots) with abnormal immature B cells (A) (red, emphasized) in patient #15 showing abnormally increased CD20 and CD34 with abnormally decreased CD38 and abnormal immature B cells (B) (red dots) in patient #10 with similar abnormal phenotype.