Recurrent chromosomal defects are found in most patients with acute nonlymphocytic leukemia.

Using a methotrexate cell synchronization technique, we have successfully studied chromosome preparations of bone marrow biopsies from 49 of 51 patients with acute nonlymphocytic leukemia (ANLL). Clonal chromosomal abnormalities were detected in 46 patients, and one of eight types of recurrent chromosomal aberrations were found in 31 patients. One of these types represents a new chromosome defect [inv(16)(p13.1q22)], found in four patients with ANLL-M2, -M4. Chromosome preparations from cultured lymphocytes of two of the four patients were analyzed for the presence of chromosome fragile sites. Both cases showed a frequent break at band 16q22, an intriguing finding that suggests a possible correlation between a fragile site and predisposition to chromosomal rearrangement in human neoplasia.