Cytogenetic study of a patient with infant acute lymphoblastic leukemia using GTG-banding and chromosome painting

Numerical and structural chromosomal abnormalities occur in up to 90% of cases of childhood acute lymphoblastic leukemia (ALL). Two-thirds of these abnormalities are recurrent. The most common abnormalities are pseudodiploidy and t(1;19), occurring 40 and 5-6% of the time. Hyperdiploidy has the best prognosis, with an 80-90% 5-year survival. The 4;11 translocation has the worst prognosis, with a 10-35% 5-year survival. We report a patient with infant acute lymphoblastic leukemia and nonrecurrent rearrangements of chromosomes 10 and 11. Structural rearrangements between chromosomes 10 and 11 have been observed in 0.5% of all cases of childhood ALL with cytogenetic abnormalities. The identification of the apparently unique structural abnormalities was achieved using fluorescent in situ hybridization (FISH) with chromosome 10- and chromosome 11-specific painting probes as an adjunct to conventional cytogenetics. As is often the case, suboptimal preparations often preclude unequivocal identification of complex rearrangements by conventional banding techniques. The cytogenetic diagnosis of our patient was established as 46,XY, der(10)-t(10;11)(p15;q14)t(10;11)(q25;p11), der(11)t(10;11)(p15;q14)t(10;11)-(q25;p11). The benefits of FISH serve to increase the resolution of detection for chromosomal abnormalities and the understanding of the pathogenic mechanisms of childhood ALL.