Immunophenotypic Pattern of Eosinophilia by Flow Cytometry
Keywords:
flow cytometry, eosinophilia, immunophenotypic pattern, granulocytes, neoplastic promyelocytes, basophils, MDSAbstract
Eosinophilia is commonly seen in variety of conditions, including infections, hypersensitivities, autoimmune disorders, idiopathic hypereosinophilic syndrome and certain neoplasms. In the latter, eosinophilia may present as a secondary (benign) component (Hodgkin lymphoma, T-cell lymphoma, acute leukemia or systemic mastocytosis) or as myeloproliferative neoplasm (MPN) characterized by clonal eosinophilic expansion. MPN with eosinophilia includes chronic eosinophilic leukemia (CEL) and MPN with rearrangement of PDGFRA, PDGFRB or FGFR1. Identification of eosinophilia by flow cytometry (FC) may be difficult due to (1) lack of eosinophil-specific immunophenotypic markers, (2) overlap of phenotypic features of eosinophils with other populations and (3) low forward scatter leading to confusion with cellular debris. Based on immunophenotypic analysis of 15 cases, here we present the FC pattern of eosinophilia easily recognizable by routine flow cytometric analysis in a clinical laboratory. Identification of eosinophilia by FC with follow-up reflex cytogenetic/FISH and/or PCR testing may be helpful to differentiate between reactive conditions and malignant eosinophilic disorders when clinically indicated.
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