Lymphoblastic transformation of chronic myelomonocytic leukemia in an infant

A 10-month-old infant with chronic myelomonocytic leukemia (CMML) of 5 months' duration, who had been treated only with transfusion, displayed leukemic transformation characterized by lymphoid morphology, PAS positivity, and myeloperoxidase negativity. Surface marker analysis of blast cells revealed expression of lymphoid-associated antigens (CD10 and CD19) but not myeloid-associated antigens (CD13, CD14, and CD33). These findings suggest that some cases of infantile CMML are clonal disorders arising in a pluripotent stem cell that can also differentiate along the lymphoid cell lineage.