B-Lymphoblastic Leukemia with BCR::ABL1-like Features After Long-term Lenalidomide Therapy

Lenalidomide, a derivative of thalidomide, is a type of immunomodulatory drug (IMiD) that has been standard therapy for multiple myeloma (MM) and other hematologic malignancies for almost two decades. The success of these drugs in MM has contributed to increased survival of patients and, as a result, patients are at risk for a secondary primary malignancy (SPM), some of which occur as a result of treatment for MM. MM patients have an increased risk for acute myeloid leukemia (AML) and Kaposi sarcoma. In addition, treatment with IMiDs is also associated with an increased risk for myelodysplastic neoplasms (MDS), squamous cell carcinoma of the skin, and, less frequently, acute lymphoblastic leukemia (ALL). We present a case of an elderly male with MM and multiple subsequent skin cancers, who presented with pancytopenia and was diagnosed with B-lymphoblastic leukemia (B-ALL) after 10 years of maintenance lenalidomide therapy.