Collaborative study of karyotypes in childhood acute lymphoblastic leukemias. Groupe Français de Cytogénétique Hématologique.

A collaborative study carried out by the Groupe Français de Cytogénétique Hématologique collected 411 successful karyotypes of childhood acute lymphoblastic leukemias. Karyotypes showed a clonal abnormality in 292 patients (71%). The distribution of ploidy groups was: pseudodiploidy in 116 karyotypes (28.2%), hyperdiploidy > 50 chromosomes in 110 karyotypes (26.8%), hyperdiploidy 47-50 chromosomes in 46 karyotypes (11.2%) and hypodiploidy in 20 karyotypes (4.9%). One-half of the patients with hyperdiploidy > 50 chromosomes also had a structural abnormality, with a partial trisomy 1q in one fourth of them. Similar translocations, candidate for new recurrent changes were identified: t(9;9)(p13;q13),t(7;9)(q11;p11),t(7;12)(q11;p12-13), t(4;12)(q13;p12), and t(1;17)(q12-21;p13). Within recurrent translocations, the three t(10;11)(p13-14;q14-21) displayed a T-cell phenotype. In T-cell leukemias, a new area of recurrent breakpoints (5q31-35) was observed and deletions 6q were more frequent in this lineage. Correlations of cytogenetic results with clinical and hematological data revealed that, within hyperdiploidy > 50 chromosomes, patients with structural changes were older than patients without. Patients with 9p changes showed some of the features usually observed in lymphomatous leukemias. Even with a short follow-up, differences in outcomes were observed. Patients with hyperdiploidy > 50 chromosomes fared the best and those with pseudodiploid karyotypes did worse than patients with other karyotypes. Patients with random translocations did not share the poor outcome of patients with recurrent translocations.