Chromosome banding studies in acute leukaemia at diagnosis.

Cytogenetic study by a chromosome banding technique has been attempted in 93 cases of acute leukaemia at diagnosis. Banding patterns were difficult to visualise in the bone-marrow chromosomes of patients with acute leukaemia because of the fuzzy appearance of the fixed metaphases. The proportion of patients with abnormal chromosomes was higher in acute lymphoblastic (ALL) than in acute myeloid (AML) leukaemia. Abnormalities were present in all cases of other cytological types. Hyperdiploidy was the most commonly found numerical error in both ALL and AML but a larger proportion of patients with ALL had hyperdiploidy in more than 30% of the cells. In ALL it was generally found that the higher the frequency of hyperdiploidy the greater was the number of chromosomes per cell. Hypodiploidy not attributable to random losses was found in only 6 patients. Clones identified by rearranged or marker chromosomes were found in all types of leukaemia. Clones marked by a 7q-chromosome, in which the break point was the same, were identified in 1 adult with ALL and 2 children with AML. The high frequency of randomly disturbed chromosomal breakage found in the bone-marrow chromosomes of a high proportion of the patients may be related to the disease process.