Chronic eosinophilic leukemia, ‘not otherwise specified’ (CEL-NOS) D47.-

Chronic eosinophilic leukemia (CEL-NOS) is classified as an MPN according to WHO 2016. It is a systemic disease with persistent autonomous eosinophilia > 1.5 G/l in the blood, which also affects the bone marrow and other organs.

CEL-NOS is always a diagnosis of exclusion, present when:

• Eosinophilia (≥ 1.5 x 109/l).
• exclusion of BCR-ABL1 positive CML, PV, ET, PMF, CNL, CMML, aCML
• Exclusion of rearrangements of PDGFRA, PDGFRB, FGFR1, no PCM1-JAK2, ETV6-JAK2 or BCR-JAK2 fusion gene.
• Blasts <20% in peripheral blood and bone marrow, and inv(16)(p13.1q22), t(16;16)(p13.1;q22), t(8;21)(q22;q22.1) and lack of other diagnostic criteria for AML
• Clonal cytogenetic or molecular alteration or blasts ≥ 2% in peripheral blood or ≥5% in bone marrow

Since clonal alterations such as TET2, ASXL1, DNMT3A mutations may also occur in a minority of elderly patients without hematologic disease, it is important to exclude other possible causes of reactive eosinophilia before making a diagnosis of CEL in the elderly based on molecular findings alone.

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