Near-haploid and low-hypodiploid acute lymphoblastic leukemia: two distinct subtypes with consistently poor prognosis

Hypodiploidy < 40 chromosomes is an uncommon genetic feature of acute lymphoblastic leukemia (ALL) in both children and adults. It has long been clear by cytogenetic analyses, and recently confirmed by mutational profiling, that these cases may be further subdivided into 2 subtypes: nearhaploid ALL with 24 to 30 chromosomes andlow-hypodiploidALLwith 31 to 39 chromosomes. Both groups are associated with a very poor prognosis, and these patients are among those who could benefit most from novel treatments.