Purpose Recurrent chromosomal abnormalities present in the leukemic cells of pediatric patients with acute lymphoblastic leukemia (ALL) often allow us to classify patients according to their prognosis, in order to establish further treatment. The dicentric translocation (9;12) consists of the rearrangement of the short arms of chromosomes 9 and 12 generating a dicentric chromosome (9;12). Patients with this alteration present a very good response to treatment and an excellent prognosis.Methods We present the case of an adolescent with ALL in which the dicentric translocation (9;12) was observed in the karyotype of the blasts at diagnosis.Results and conclusion Given the excellent results of our patient and most of the series published to date, an international study is necessary to determine the true prognostic significance of this molecular alteration.