T-cell blast crisis in chronic myelogenous leukemia - Immunophenotypic and molecular biologic findings

T-cell blast crisis in chronic myelogenous leukemia is rare. We examined three patients (ages 35 to 72 years) in whom T-cell blast crisis developed 11 to 36 months (mean, 25 months) after diagnosis of chronic myelogenous leukemia and who died 4 to 12 months (mean, 7 months) thereafter. Two patients had diffuse lymphadenopathy, and the third had marked lymphocytosis (white blood cell count 217,000/mu L, with 90% circulating blasts). In all three patients, neoplastic cells had the appearance of lymphoblasts and were immunoreactive for T-cell markers by immunohistochemical or flow cytometric analysis or both. Molecular diagnostic studies revealed the presence of a bcr-abl oncogene rearrangement in all three cases, but none exhibited a clonal T-cell receptor partial derivative, beta, gamma chain gene rearrangement. One case exhibited deletion of the J partial derivative 1 region of both partial derivative chain genes. The significance of these findings is discussed, and they are compared with those of other reported cases of T-cell blast crisis in chronic myelogenous leukemia.