T-cell acute lymphoblastic leukemia relapsing as acute myelomonocytic leukemia and terminating possibly as chronic myelocytic leukemia.

A 9-year-old boy suffering from T-cell acute lymphoblastic leukemia (T-ALL) with a mediastinal mass had a complete remission as a result of treatment. Ten months later, he developed a typical acute myelomonocytic leukemia (AMMoL) pattern. Two months after a second relapse, he showed a clinical picture that was indistinguishable from chronic myelocytic leukemia (CML). At autopsy, massive infiltration of CML-like cells was observed even in the thymus (190 g). These observations suggest that the leukemia in this child arose in a pluripotent stem cell capable of differentiation into both T-lymphocytic and myelomonocytic lineages.