Clonal Hematopoiesis Without Malignant Transformation Lasting Over 2 Years in a 9-Year-old Boy, Following Treatment for Acute Lymphocytic Leukemia.

Children with acute lymphocytic leukemia rarely develop secondary hematological neoplasms. A 5-year-old boy was diagnosed with standard-risk precursor B-cell acute lymphocytic leukemia. The patient exhibited aberrant chromosomal changes in the bone marrow at 6 months postchemotherapy: 46,XY,der(6) t(1;6)(q12;p22) dup(6)(p22p12)[15]. Clinically, the patient has sustained complete remission and has not developed myeloid malignancy over the subsequent period (27 mo). The cytogenetic aberration was observed in 11% of CD34+ cells isolated from the bone marrow. We infer that the abnormal clone acquires self-renewal potency, differentiation, and growth advantage. Further long-term observation is needed to determine the nature of this cytogenetic aberration.