Dic(9;20)(p13;q11)-positive B-cell precursor acute lymphoblastic leukemia: A genetic and clinical entity?

Cytogenetically defined dic(9;20)-positive leukemia accounts for ˜2% of pediatric BCP-ALL and is considered as unique genetic and clinical entity. However, at the molecular level the breakpoints in both chromosomes are heterogeneous, and thus, the formation of a dic(9;20) does not result in the expression of a consistent fusion gene. Hence, a dic(9;20) is generally associated with loss of genetic material, primarily hetero- or even homozygous deletion of CDKN2A/B (9p21), disruption or deletion of PAX5 (9p13) and ASXL1 (20q11), but rarely with a PAX5-C20orf112 fusion gene.