Acute lymphoblastic leukemia with hypereosinophilia and 9p21 deletion: case report and review of the literature.

Acute lymphoblastic leukemia (ALL) associated with eosinophilia is very rare, with approximately 44 reported cases. We are reporting this case not only because of the rarity of ALL with peripheral blood eosinophilia, but also because we observed a homozygous deletion of the 9p21 locus corresponding to the p16 gene, a cytogenetic abnormality that was not reported in other documented cases. ALL with eosinophilia must be considered a distinct clini-copathologic entity. It is very important for clinicians to be aware of this specific manifestation of ALL within the context of a persistent peripheral eosinophilia, particularly if no lymphoblasts are present in the peripheral blood.