Chronic Eosinophilic Leukemia, NOS

Differential Diagnosis

Hypereosinophilia*

	Idiopathic Hypereosinophilia	Idiopathic Hypereosinophilic Syndrome	Chronic Eosinophilic Leukemia NOS	Hematolymphoid Neoplasms with Specific Genetic Abnormalities#
Hypereosinophilia	Yes	Yes	Yes	Yes
Tissue Damage	No	Yes	Subset	Subset
Clonality**	No	Not demonstrated	Yes	Yes
Blasts ≥20%	No	No	No	Subset
Abnormalities of BCR-ABL1, PDGFRA, PDGFRB, KIT, FGFR1 or CBFB	No	No	No	Yes

*Transient, reactive and secondary eosinophilia must be excluded
- Causes of reactive eosinophilia, including
  - Drug reaction
  - Allergy, including bronchopulmonary aspergillosis
  - Parasites
  - Loeffler syndrome
  - Collagen vascular diseases
  - Kimura disease
  - Vasculitis
  - Cyclical eosinophilia
- Aberrant T cell population associated eosinophilia
  - Also known as lymphocyte variant hypereosinophilia
  - Abnormal T cell population does not meet diagnostic criteria for leukemia or lymphoma
- Causes of eosinophilia secondary to neoplasms
  - T cell lymphomas and leukemias
  - Hodgkin lymphoma
  - Systemic mastocytosis
#Neoplasms with specific genetic abnormalities are covered separately:
- CML (rarely with predominant hypereosinophilia) if BCR-ABL1
- Hematolymphoid neoplasms with abnormalities of PDGFRA, PDGFRB, FGFR1
- AML-M4eo (with inv or t(16)(p13.1;q22) CBFB-MYH11)
- Systemic mastocytosis (KIT)
**Clonality may be demonstrated by cytogenetics or assumed due to >2% PB or >5% BM blasts or dysplastic features