[T lymphoid blast crisis of Philadelphia chromosome-positive chronic myeloid leukemia: analysis of 3 cases].

BACKGROUND

To investigate the frequency of the T lymphoid phenotype in the blast crisis of chronic myelocytic leukemia (CML) with positive Philadelphia chromosome (Ph) and to evaluate the major clinical and hematologic features of the patients with this phenotype.

METHODS

The presence of the TdT enzyme was assessed and specific monoclonal antibodies to the different hemopoietic lines were used to evaluate blast cells in 38 patients with blast crisis during Ph-positive CML.

RESULTS

T lymphoid phenotype was found in three of the 38 patients, corresponding in all cases to immature T cells. In one patient, the blast crisis was the presenting feature of CML and in two the localization of the blast crisis was lymphadenopathic. In the two patients who could be followed up a favorable response to chemotherapy regimens including vincristine and prednisone was observed.

CONCLUSIONS

Although uncommon, T lymphoid blast crisis in CML should no longer be considered exceptional. This phenotypic finding suggests that, at least in some cases, CML originates in a pluripotential stem cell common to all hemopoietic cells, including T lymphocytes.