Hypodiploidy is associated with a poor prognosis in childhood acute lymphoblastic leukemia.

Leukemic cells from 31 (7.6%) of 409 children with newly diagnosed acute lymphoblastic leukemia (ALL) had a hypodiploid karyotype. The patients' ages ranged from 0.8 to 17 years (median, 5 years) and their initial leukocyte counts from 1.0 to 132 X 10(9)/L (median, 12.7 X 10(9)/L). Modal chromosome numbers for the leukemic stem lines were 45 in 26 cases, 28 in two cases, and 26, 36 and 43 in one case each. Seven cases had one to three additional abnormal lines due to clonal evolution. Chromosome 20 was lost most frequently (nine cases). Structural abnormalities--including chromosomal translocations (21 cases), deletions (ten cases), duplications (two cases), or inversions (one case)--were common findings; the nonrandom translocations consisted of the t(1;19)(q23;p13.3) in two pre-B cases and tdic(9;12)(p1?1;p1?2) in three cases of common ALL. When compared with hyperdiploid cases (greater than 50 chromosomes), ALL with hypodiploidy was found to have a poorer outcome and was more likely to be associated with chromosomal translocations, higher serum lactic dehydrogenase levels, and age less than 2 or greater than or equal to 10 years. Moreover, patients with hypodiploid ALL fared as poorly as those with pseudodiploid karyotypes, even though their leukocyte counts and serum lactic dehydrogenase levels were lower and they had a comparable frequency of leukemic cell translocations. Hypodiploidy is therefore an unfavorable karyotypic feature in childhood ALL.