[High hyperdiploid acute lymphoblastic leukemia is a highly curable subtype of childhood leukemia]

Acute lymphoblastic leukemia (ALL) is the most frequent malignancy in children. In Hungary 60-70 new cases are diagnosed annually. The survival rate is 85-90% in developed countries with current treatment protocols. The most common genetic category of childhood ALL is the high hyperdiploid subtype (HHD) with chromosome numbers of 51 to 67. It accounts for approximately 25% of all cases. The prognosis is very good, though relapse occurs in ~15% of cases and there are data on the heterogeneity of this subgroup as well. In this paper we give an overview of the cytogenetic, clinical, epidemiological and prognostic features of this subgroup. We also demonstrate our interphase fluorescent in situ hybridization (iFISH) analysis performed retrospectively on 168 untreated bone marrow samples of precursor B pediatric ALL patients to reveal the numerical aberrations of chromosomes 4, 6, 10, 14, 17, 18, 21 and X, which are most frequently affected by gain in HHD ALL. Data from 48 high hyperdiploid patients indicated that high modal number (>55 chromosomes) and specific chromosomal gains (+4, +4/+6, +4/+17, +4/+18) exhibited significance in terms of beneficial overall survival.