Clinical significance of the cytogenetics of acute leukemias.

Numerous chromosome abnormalities are repeatedly found in the acute leukemias. These abnormalities have both diagnostic and prognostic utility. Some abnormalities, such as the t(4;11) (q21;q23) and t(9;22) (q34;q11) are found in both lymphoid and myeloid leukemias. In both disorders, these rearrangements are associated with a poor prognosis. Some abnormalities are found exclusively in myeloid malignancies, e.g., the t(8;21) (q22;q22) and rearrangements of chromosome 16q22, both of which carry a good prognosis. Other abnormalities are found only in lymphoid malignancies, like those of chromosome 14 at band q11 which involve T lymphoblasts. T-cell receptor (TRC) genes have been mapped to the 14q11 band. Recombinations involving the TCR alpha gene and the myc oncogene have been found in the t(8;14) (q24;q11). Similar involvement of immunoglobulin heavy chain genes and the myc oncogene has been well documented in molecular studies of B-cell lymphoma patients with a t(8;14) (q24;q32).