FISH-Guided Evaluation of Hyperdiploidy and Other Cytogenetic Abnormalities in Childhood Burkitt Lymphoma

Background: Burkitt lymphoma (BL) is the most common lymphoma in childhood. Apart from MYC rearrangement, considered the hallmark of the disease, BL often presents with additional chromosome aberrations, the biological and clinical significance of which is not fully understood. Materials and methods: The study included 72 children (55 boys, 17 girls), aged 2-16 years (median 9), with BL diagnosed on the basis of histopathology and a demonstrable MYC rearrangement. Touch imprints from the diagnostic biopsy samples were investigated with i-FISH for MYC, BCL2, BCL6, IGH, IGK and IGL rearrangements genes and copy number aberrations involving 1q21/1p32, 7cen/7q31, 9cen/9p21, 13q14/13q34 and 17cen/17p13. Deviations from the diploid status were further investigated for aneusomies of the carrier chromosome with the use of appropriate chromosome enumeration probes. Results: MYC gene was demonstrated in all cases with MYC/IGH fusion in 83.3% (60/72). 47 cases (65.3%) were found with least one additional aberration, most commonly with 1q gain (29.2%), 7q gain (19.4%), 13q deletion (19.4%), hemizygous 9p loss (8.3%) and hyperdiploidy (8.3%). Advanced clinical stage (IV), 7q gain (but not trisomy 7) and -9/9p- were significantly associated with shorter overall survival. There was no instance of relapse or death among the hyperdiploid cases. Conclusions: This extensive FISH investigation on imprints of affected tissue provides clinically meaningful information on the genetic profile of BL and may prove valuable in the management of patients with no karyotype available. In particular, the demonstration of hyperdiploidy through the use of chromosome enumeration probes could offer the means for the delineation of clonal evolution pathways and the recognition of a subgroup of children with excellent prognosis who could be cured with low-intensity chemotherapy regimens.