Cytogenetic study of 105 children with acute lymphoblastic leukemia.

Cytogenetic analysis was performed on 105 children with acute lymphoblastic leukemia (ALL). Adequate mitoses for study were obtained in 79 of the cases (71%). A normal karyotype was found in 18 patients (23%), while clonal chromosomal abnormalities were detected in 61 patients (77%). The karyotypes fell into five categories according to modal number: normal (18 patients), pseudodiploid (27 patients), hypodiploid (3 patients), hyperdiploid with 47-50 chromosomes (11 patients), and hyperdiploid with greater than or equal to 51 chromosomes (20 patients). Structural chromosome changes were found in 50 patients (63%); translocations were encountered in 15 of these patients (19%). The chromosome most often participating in translocations was number 19. Modal number was found to be an independent prognostic factor. Modal numbers 47-50 were associated with the poorest prognosis. The hyperdiploid clone with more than 50 chromosomes and the normal karyotype had the best prognosis.