[Incidence and distribution of t(12;21) in prognostic groups of pediatric acute lymphoblastic leukemia]. / A t(12;21) incidenciája és megoszlása a gyermekkori akut lymphoblastos leukaemia prognosztikai csoportjaiban.

The authors investigated by reverse transcription-polymerase chain reaction the incidence of the t(12;21)(p13;q22) translocation among 130 pediatric acute lymphoblastic leukemia registered by the Hungarian Pediatric Oncology Workgroup. The distribution of this translocation was analysed in the ploidy categories as defined by the flow cytometric DNA analysis and interphase cytogenetics. The incidence of the translocation proved to 19%, the positive patients' age ranged between 2 and 14 with an average of 5.8 years. Ninety percent of the leukemic patients harbouring the t(12;21) exhibited the precursor B-cell phenotype, 10% coexpressed myeloid markers. Coexistence of the t(12;21) with the m-bcr type of Philadelphia translocation was not observed. Ninety five percent of the t(12;21) positive children was diploid by flow cytometry whereas the same figure proved to be 58% using interphase cytogenetics. This difference was due to the hypo- and pseudodiploidy undetectable by flow cytometry but revealed by interphase cytogenetics. The authors conclude that the t(12;21) positive patients which seemed to be homogeneous at gross DNA level were markedly heterogeneous with interphase cytogenetics and this might explain the inconsistent data in the literature in connection with prognostic significance of the t(12;21).