Clinical course of lenalidomide-associated ALL in one patient. (A) Clinical course of patient #9, who was found to have an immature B-cell population with B-ALL immunophenotype at 48 months into lenalidomide maintenance for MM, with regression of B-ALL after lenalidomide withdrawal and subsequent progression to overt B-ALL at 284 days from the initial finding of abnormal B lymphoblasts. He received B-ALL therapy consisting of hyper-CVAD followed by blinatumomab and achieved CR with MRD negativity, followed by haploidentical allogeneic HCT and remains in continuous, ongoing MRD⁻ CR. Flow cytometry plots from BMAs and TdT immunostains on core biopsies depict evolution in B-lymphoblast population from initial finding 48 months into lenalidomide maintenance (B,E) to regression after lenalidomide withdrawal (C,F) to overt progression to B-ALL (D,G). All blast percentages are from BMAs.