Chronic myeloid leukemia arising in a progenitor common to T cells and myeloid cells

Until recently, T cells were believed not to be involved in chronic myeloid leukemia. We describe an example of CML in T lymphoblastic crisis with massive generalized lymphadenopathy in which the blasts were CD2(+), CD5(+), and CD7(+), variably CD1(+) and CD3(+), and both responded to and could be induced to produce the T cell growth factor, interleukin-2. Additionally, the blasts were shown to contain the CML-related tyrosine kinase P210bcr-abl rather than the smaller kinase associated with Ph1(+) ALL. Finally, the participation of the T lymphoid lineage in the CML clone was proven by the presence of the same BCR rearrangement in blasts as in granulocytes, suggesting the existence of a bone marrow progenitor common to the T cell and myeloid lineages.