Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (339 page)

   No BCR-ABL1 gene rearrangement.

   No PDGFRA, PDGFRB, or FGFR1 gene rearrangements.

   Evidence of clonality by either cytogenetic or molecular studies, or blast cells are >2% in the peripheral blood or >5% in the bone marrow.

   Neoplasms With Eosinophilia and Abnormalities of PDGFRA , PDGFRB, or FGFR2

Involve rearrangement of tyrosine kinase gene. PDGFRA and PDGFRB rearrangements common in CEL; PDGFRB rearrangements can be detected with routine cytogenetic analysis, PDGFRA is typically cryptic and require FISH for detection.

   Who Should Be Suspected?

Patients with eosinophilia for longer than 6 months. Presumptive signs and symptoms of organ involvement, especially cardiac or neurologic.

   Laboratory Findings

   CBC in CEL:

   Eosinophilia with mostly mature eosinophils; the WBC count is usually <25,000/μL but may be >90,000, with rare immature forms.

   Mild anemia in half the patients; thrombocytopenia in one third of cases; thrombocytosis may also be present.

   Increase in dysplastic-appearing or immature eosinophils.

   Bone marrow:

   Hypercellular marrow with 25–75% of eosinophils and increase in eosinophil precursors; no reticulin fibrosis.

   Hyperplasia with increase in abnormal eosinophils and eosinophilic precursors.