All patients with acute nonlymphocytic leukemia may have a chromosomal defect.

Previous studies of banded marrow chromosomes suggest that half the patients with acute nonlymphocytic leukemia (ANLL) have normal karyotypes. To determine whether high-resolution chromosome analysis could detect additional abnormalities, we studied marrow from 26 patients with ANLL, using methotrexate cell synchronization as well as a direct technique. In 24 patients, including 18 who were untreated, adequate mitoses were obtained. All demonstrated clonal chromosomal abnormalities, which involved a balanced translocation in 11 cases, a complete or partial monosomy in 10, and a trisomy in six. Previously reported recurring defects in ANLL were identified, including t(15;17) in two cases, -7 in two cases, and +8 in three cases. In addition, a new specific abnormality involving band 11q23 was noted in one patient with acute monocytic leukemia and in two with myelomonocytic leukemia. Our results suggest that most, if not all, patients with ANLL have chromosomal changes, and that our new technique may allow more precise identification of subtypes of ANLL with characteristic clinical and hematologic features.