Eosinophilic leukemia: a myeloproliferative disorder distinct from the hypereosinophilic syndrome.

Evidence to support the existence of eosinophilic leukemia (EL) as an autonomous eosinophilic proliferation analogous to other myeloproliferative disorders has been somewhat confusing. Partially obscuring the existence of EL as a distinct entity is the proposal that EL merely represents a clinically aggressive form of hypereosinophilic syndrome. This report details the clinical and pathologic findings in a case of EL. The presence of trisomy 8 and trisomy 21; morphologic, cytochemical, and ultrastructural findings of granular abnormalities and nuclear/cytoplasmic dysynchrony; and a clinical course similar to that of other myeloproliferative disorders support the existence of EL as a rare but distinct entity within the spectrum of myeloproliferative diseases.