HAEM5:Chronic eosinophilic leukaemia

Haematolymphoid Tumours (WHO Classification, 5th ed.)

editContent Update To WHO 5th Edition Classification Is In Process; Content Below is Based on WHO 4th Edition Classification

This page was converted to the new template on 2023-12-07. The original page can be found at HAEM4:Chronic Eosinophilic Leukemia, Not Otherwise Specified.

(General Instructions – The focus of these pages is the clinically significant genetic alterations in each disease type. This is based on up-to-date knowledge from multiple resources such as PubMed and the WHO classification books. The CCGA is meant to be a supplemental resource to the WHO classification books; the CCGA captures in a continually updated wiki-stye manner the current genetics/genomics knowledge of each disease, which evolves more rapidly than books can be revised and published. If the same disease is described in multiple WHO classification books, the genetics-related information for that disease will be consolidated into a single main page that has this template (other pages would only contain a link to this main page). Use HUGO-approved gene names and symbols (italicized when appropriate), HGVS-based nomenclature for variants, as well as generic names of drugs and testing platforms or assays if applicable. Please complete tables whenever possible and do not delete them (add N/A if not applicable in the table and delete the examples); to add (or move) a row or column in a table, click nearby within the table and select the > symbol that appears. Please do not delete or alter the section headings. The use of bullet points alongside short blocks of text rather than only large paragraphs is encouraged. Additional instructions below in italicized blue text should not be included in the final page content. Please also see Author_Instructions and FAQs as well as contact your Associate Editor or Technical Support.)

Primary Author(s)*

Chelsea D. Kramish; Daynna J.Wolff

Pending Review*

WHO Classification of Disease

Structure	Disease
Book	Haematolymphoid Tumours (5th ed.)
Category	Myeloid proliferations and neoplasms
Family	Myeloproliferative neoplasms
Type	Myeloproliferative neoplasms
Subtype(s)	Chronic eosinophilic leukaemia

Related Terminology

Acceptable	Chronic eosinophilic leukaemia NOS
Not Recommended	N/A

Gene Rearrangements

Put your text here and fill in the table (Instructions: Details on clinical significance such as prognosis and other important information can be provided in the notes section. Please include references throughout the table. Do not delete the table.)

Driver Gene	Fusion(s) and Common Partner Genes	Molecular Pathogenesis	Typical Chromosomal Alteration(s)	Prevalence -Common >20%, Recurrent 5-20% or Rare <5% (Disease)	Diagnostic, Prognostic, and Therapeutic Significance - D, P, T	Established Clinical Significance Per Guidelines - Yes or No (Source)	Clinical Relevance Details/Other Notes
EXAMPLE: ABL1	EXAMPLE: BCR::ABL1	EXAMPLE: The pathogenic derivative is the der(22) resulting in fusion of 5’ BCR and 3’ABL1.	EXAMPLE: t(9;22)(q34;q11.2)	EXAMPLE: Common (CML)	EXAMPLE: D, P, T	EXAMPLE: Yes (WHO, NCCN)	EXAMPLE: The t(9;22) is diagnostic of CML in the appropriate morphology and clinical context (add reference). This fusion is responsive to targeted therapy such as Imatinib (Gleevec) (add reference). BCR::ABL1 is generally favorable in CML (add reference).
EXAMPLE: CIC	EXAMPLE: CIC::DUX4	EXAMPLE: Typically, the last exon of CIC is fused to DUX4. The fusion breakpoint in CIC is usually intra-exonic and removes an inhibitory sequence, upregulating PEA3 genes downstream of CIC including ETV1, ETV4, and ETV5.	EXAMPLE: t(4;19)(q25;q13)	EXAMPLE: Common (CIC-rearranged sarcoma)	EXAMPLE: D		EXAMPLE: DUX4 has many homologous genes; an alternate translocation in a minority of cases is t(10;19), but this is usually indistinguishable from t(4;19) by short-read sequencing (add references).
EXAMPLE: ALK	EXAMPLE: ELM4::ALK Other fusion partners include KIF5B, NPM1, STRN, TFG, TPM3, CLTC, KLC1	EXAMPLE: Fusions result in constitutive activation of the ALK tyrosine kinase. The most common ALK fusion is EML4::ALK, with breakpoints in intron 19 of ALK. At the transcript level, a variable (5’) partner gene is fused to 3’ ALK at exon 20. Rarely, ALK fusions contain exon 19 due to breakpoints in intron 18.	EXAMPLE: N/A	EXAMPLE: Rare (Lung adenocarcinoma)	EXAMPLE: T		EXAMPLE: Both balanced and unbalanced forms are observed by FISH (add references).
EXAMPLE: ABL1	EXAMPLE: N/A	EXAMPLE: Intragenic deletion of exons 2–7 in EGFR removes the ligand-binding domain, resulting in a constitutively active tyrosine kinase with downstream activation of multiple oncogenic pathways.	EXAMPLE: N/A	EXAMPLE: Recurrent (IDH-wildtype Glioblastoma)	EXAMPLE: D, P, T

editv4:Chromosomal Rearrangements (Gene Fusions)

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No single or specific genetic abnormality has been identified in CEL, NOS. Rearrangement of PDGFRA, PDGFRB, or FGFR1 excludes the diagnosis of CEL, NOS. PCM1-JAK2, ETV6-JAK2, or BCR-JAK2 are also specifically excluded. [1] Three unique cases of myeloid/lymphoid neoplasm with eosinophilia have shown FLT3 rearrangement: one with t(13;14)(q12;q32)/TRIP11-FLT3 rearrangement, and two with ETV6-FLT3. Eosinophilia and FLT3 rearrangement typically shows myeloproliferative neoplasms, most frequently CEL, NOS, and T-ALL. [5] A unique case of CEL,NOS with a novel fusion gene between exon 22 of GCC2 and exon 12 of PDGFRB was detected and confirmed by PCR in a 54 year old man presenting with cough and dyspnea. [6]

Chromosomal Rearrangement	Genes in Fusion (5’ or 3’ Segments)	Pathogenic Derivative	Prevalence
EXAMPLE: t(9;22)(q34;q11.2)	EXAMPLE: 3'ABL1 / 5'BCR	EXAMPLE: der(22)	EXAMPLE: 5%
EXAMPLE: t(8;21)(q22;q22)	EXAMPLE: 5'RUNX1 / 3'RUNXT1	EXAMPLE: der(8)	EXAMPLE: 5%

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editv4:Clinical Significance (Diagnosis, Prognosis and Therapeutic Implications).

Please incorporate this section into the relevant tables found in:

• Chromosomal Rearrangements (Gene Fusions)
• Individual Region Genomic Gain/Loss/LOH
• Characteristic Chromosomal Patterns
• Gene Mutations (SNV/INDEL)

Although survival is variable, acute transformation is common and prognosis is typically poor. The median survival time in one small series was 22.2 months. Response to imatinib has been reported but is uncommon. Treatment with Interferon alpha leading to cytogenic remission has been reported in 3 cases with translocations with a 5q31-33 breakpoint. Complete hematologic response has been achieved in one reported case of CEL with ETV6/FLT3 fusion, with the off-label use of FLT3-inhibitor, sorafenib.[2] Unfavorable prognostic findings include marked splenomegaly, blasts in the blood or increased blasts in bone marrow, cytogenetic abnormalities, and dysplastic features in other myeloid lineages. [1] According to a study of 17 cases defined by WHO-2016 standards, univariate survival analysis showed predictors of inferior survival included megakaryocytic atypia (P = .01), peripheral blood eosinophilic atypia (P = .024), LDH (P = .046) and abnormal karyotype (P = .020). [4] Of these patients, the most frequently utilized first line agents were hydroxyurea as a single agent or in combination with steroids, steroids as a single agent, or in combination. Half of patients treated with hydroxyurea based regimens responded with a persistent decline in eosinophil count over 17.5 months. Approximately one third of patients demonstrated response to steroids for a median duration of 13 months. Three of these patients were treated with imatinib of which two had normalization of eosinophil count. [4] Imatinib was successful in treatment of the individual case of CEL,NOS with novel fusion gene involving PDGFRB and GCC2 with disappearance of the fusion gene in bone marrow after three months. [6]

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Individual Region Genomic Gain/Loss/LOH

Put your text here and fill in the table (Instructions: Includes aberrations not involving gene rearrangements. Details on clinical significance such as prognosis and other important information can be provided in the notes section. Can refer to CGC workgroup tables as linked on the homepage if applicable. Please include references throughout the table. Do not delete the table.)

Chr #	Gain, Loss, Amp, LOH	Minimal Region Cytoband and/or Genomic Coordinates [Genome Build; Size]	Relevant Gene(s)	Diagnostic, Prognostic, and Therapeutic Significance - D, P, T	Established Clinical Significance Per Guidelines - Yes or No (Source)	Clinical Relevance Details/Other Notes
EXAMPLE: 7	EXAMPLE: Loss	EXAMPLE: chr7	EXAMPLE: Unknown	EXAMPLE: D, P	EXAMPLE: No	EXAMPLE: Presence of monosomy 7 (or 7q deletion) is sufficient for a diagnosis of AML with MDS-related changes when there is ≥20% blasts and no prior therapy (add reference).  Monosomy 7/7q deletion is associated with a poor prognosis in AML (add references).
EXAMPLE: 8	EXAMPLE: Gain	EXAMPLE: chr8	EXAMPLE: Unknown	EXAMPLE: D, P		EXAMPLE: Common recurrent secondary finding for t(8;21) (add references).
EXAMPLE: 17	EXAMPLE: Amp	EXAMPLE: 17q12; chr17:39,700,064-39,728,658 [hg38; 28.6 kb]	EXAMPLE: ERBB2	EXAMPLE: D, P, T		EXAMPLE: Amplification of ERBB2 is associated with HER2 overexpression in HER2 positive breast cancer (add references). Add criteria for how amplification is defined.

editv4:Genomic Gain/Loss/LOH

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Chromosome Number	Gain/Loss/Amp/LOH	Region
EXAMPLE: 8	EXAMPLE: Gain	EXAMPLE: chr8:0-1000000
EXAMPLE: 7	EXAMPLE: Loss	EXAMPLE: chr7:0-1000000

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Characteristic Chromosomal or Other Global Mutational Patterns

Put your text here and fill in the table (Instructions: Included in this category are alterations such as hyperdiploid; gain of odd number chromosomes including typically chromosome 1, 3, 5, 7, 11, and 17; co-deletion of 1p and 19q; complex karyotypes without characteristic genetic findings; chromothripsis; microsatellite instability; homologous recombination deficiency; mutational signature pattern; etc. Details on clinical significance such as prognosis and other important information can be provided in the notes section. Please include references throughout the table. Do not delete the table.)

Chromosomal Pattern	Molecular Pathogenesis	Prevalence - Common >20%, Recurrent 5-20% or Rare <5% (Disease)	Diagnostic, Prognostic, and Therapeutic Significance - D, P, T	Established Clinical Significance Per Guidelines - Yes or No (Source)	Clinical Relevance Details/Other Notes
EXAMPLE: Co-deletion of 1p and 18q	EXAMPLE: See chromosomal rearrangements table as this pattern is due to an unbalanced derivative translocation associated with oligodendroglioma (add reference).	EXAMPLE: Common (Oligodendroglioma)	EXAMPLE: D, P
EXAMPLE: Microsatellite instability - hypermutated		EXAMPLE: Common (Endometrial carcinoma)	EXAMPLE: P, T

editv4:Characteristic Chromosomal Aberrations / Patterns

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A recurrent karyotypic abnormality typically observed in myeloid disorders such as gain of chromosome 8, loss of chromosome 7 or isochromosome 17q supports a diagnosis as well as the presence of a translocation. [1] [1] Morsia et al demonstrated cytogenetic abnormalities in 15 of 17 (88.2%) patients diagnosed with CEL, NOS including trisomy 8 (n = 4), and complex karyotype (n = 3). [4]

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Gene Mutations (SNV/INDEL)

Put your text here and fill in the table (Instructions: This table is not meant to be an exhaustive list; please include only genes/alterations that are recurrent or common as well either disease defining and/or clinically significant. If a gene has multiple mechanisms depending on the type or site of the alteration, add multiple entries in the table. For clinical significance, denote associations with FDA-approved therapy (not an extensive list of applicable drugs) and NCCN or other national guidelines if applicable; Can also refer to CGC workgroup tables as linked on the homepage if applicable as well as any high impact papers or reviews of gene mutations in this entity. Details on clinical significance such as prognosis and other important information such as concomitant and mutually exclusive mutations can be provided in the notes section. Please include references throughout the table. Do not delete the table.)

Gene	Genetic Alteration	Tumor Suppressor Gene, Oncogene, Other	Prevalence - Common >20%, Recurrent 5-20% or Rare <5% (Disease)	Diagnostic, Prognostic, and Therapeutic Significance - D, P, T	Established Clinical Significance Per Guidelines - Yes or No (Source)	Clinical Relevance Details/Other Notes
EXAMPLE:EGFR	EXAMPLE: Exon 18-21 activating mutations	EXAMPLE: Oncogene	EXAMPLE: Common (lung cancer)	EXAMPLE: T	EXAMPLE: Yes (NCCN)	EXAMPLE: Exons 18, 19, and 21 mutations are targetable for therapy. Exon 20 T790M variants cause resistance to first generation TKI therapy and are targetable by second and third generation TKIs (add references).
EXAMPLE: TP53; Variable LOF mutations	EXAMPLE: Variable LOF mutations	EXAMPLE: Tumor Supressor Gene	EXAMPLE: Common (breast cancer)	EXAMPLE: P		EXAMPLE: >90% are somatic; rare germline alterations associated with Li-Fraumeni syndrome (add reference). Denotes a poor prognosis in breast cancer.
EXAMPLE: BRAF; Activating mutations	EXAMPLE: Activating mutations	EXAMPLE: Oncogene	EXAMPLE: Common (melanoma)	EXAMPLE: T

Note: A more extensive list of mutations can be found in cBioportal, COSMIC, and/or other databases. When applicable, gene-specific pages within the CCGA site directly link to pertinent external content.

editv4:Gene Mutations (SNV/INDEL)

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JAK2 mutations have been identified, however mutations in ASXL1, TET2 and EZH2 appear to be common. [1] The study by Morsia et al. of 17 CEL patients demonstrated two patients each with 13q, 20q deletion, and chromosome 1 abnormalities, one patient with monosomy 7 and one with 3q deletion. All seven patients with NGS studies harbored one or more mutations; ASXL1 (42.9%); IDH1 (28.6%), and one each (14.3%) with TP53, SRSF2, SH2B3, STAT5B, KDM6A and NF1 mutations. [4] A novel JAK2 exon 13 insertion/deletion mutant has been identified and described by Patel et al. in a patient fulfilling diagnostic criteria for both PV and CEL. This study demonstrated that JAK2ex13InDel bears mechanistic resemblance to JAK2V617F but can activate STAT5 in the absence of βc family cytokines IL-3, IL-5, and GM-CSF, potentially promoting eosinophilic differentiation. [7] Keleman et al. discussed STAT5B mutations as reported in four cases: two cases of CEL, NOS; one case of CMML with eosinophilia; and one case of MDS with eosinophilia, respectively. While the presence of a STAT5B N642H mutation may be a potential marker of chronic eosinophilic neoplasms, similar mutations have been described in nonclonal HE and may not be independently sufficient to establish a diagnosis of CEL, NOS. [8]

Gene	Mutation	Oncogene/Tumor Suppressor/Other	Presumed Mechanism (LOF/GOF/Other; Driver/Passenger)	Prevalence (COSMIC/TCGA/Other)
EXAMPLE: TP53	EXAMPLE: R273H	EXAMPLE: Tumor Suppressor	EXAMPLE: LOF	EXAMPLE: 20%

Other Mutations

Type	Gene/Region/Other
Concomitant Mutations	EXAMPLE: IDH1 R123H
Secondary Mutations	EXAMPLE: Trisomy 7
Mutually Exclusive	EXAMPLE: EGFR Amplification

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Genes and Main Pathways Involved

Put your text here and fill in the table (Instructions: Please include references throughout the table. Do not delete the table.)

Gene; Genetic Alteration	Pathway	Pathophysiologic Outcome
EXAMPLE: BRAF and MAP2K1; Activating mutations	EXAMPLE: MAPK signaling	EXAMPLE: Increased cell growth and proliferation
EXAMPLE: CDKN2A; Inactivating mutations	EXAMPLE: Cell cycle regulation	EXAMPLE: Unregulated cell division
EXAMPLE: KMT2C and ARID1A; Inactivating mutations	EXAMPLE: Histone modification, chromatin remodeling	EXAMPLE: Abnormal gene expression program

editv4:Genes and Main Pathways Involved

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Genetic Diagnostic Testing Methods

A detailed history, physical exam, blood count and examination of blood smear are key diagnostic measures. The process of making a diagnosis heavily relies on the exclusion of reactive eosinophilia, and myeloid neoplasms with the previously mentioned rearrangements or fusions. [1] Wang et al. demonstrated that targeted next generation sequencing helps to establish clonality in a portion of patients with hypereosinophilia that would otherwise be diagnosed with idiopathic hypereosinophilic syndrome. [3]

Links

https://ccga.io/index.php/Chronic_Eosinophilic_Leukemia,_Not_Otherwise_Specified?veaction=edit&section=2

References

1. Bain B.J, et al., (2017). Chronic eosinophilic leukemia, NOS, in World Health Organization Classification of Tumours of Haematopoietic and Lymphoid Tissues, Revised 4th edition. Swerdlow SH, Campo E, Harris NL, Jaffe ES, Pileri SA, Stein H, Thiele J, Arber DA, Hasserjian RP, Le Beau MM, Orazi A, and Siebert R, Editors. IARC Press: Lyon, France, p54-56
2. Ricci, F., Balducci, S., Guerrini, F., Grassi, S., Ciabatti, E., Baratè, C., . . . Galimberti, S. (2020). Sorafenib Induced Complete Cytogenetic and Molecular Response in a Chronic Eosinophilic Leukemia Case with t(12;13) Translocation. Clinical Hematology International, 2. doi:10.2991/chi.k.200714.001
3. Wang SA, Tam W, Tsai AG, Arber DA, Hasserjian RP, Geyer JT, George TI, Czuchlewski DR, Foucar K, Rogers HJ, Hsi ED, Bryan Rea B, Bagg A, Dal Cin P, Zhao C, Kelley TW, Verstovsek S, Bueso-Ramos C, Orazi A. Targeted next-generation sequencing identifies a subset of idiopathic hypereosinophilic syndrome with features similar to chronic eosinophilic leukemia, not otherwise specified. Mod Pathol. 2016 Aug;29(8):854-64. doi: 10.1038/modpathol.2016.75. Epub 2016 May 13. PMID: 27174585.
4. Morsia, E., Reichard, K., Pardanani, A., Tefferi, A., & Gangat, N. (2020). WHO defined chronic eosinophilic leukemia, not otherwise specified ( CEL , NOS ): A contemporary series from the Mayo Clinic. American Journal of Hematology, 95(7). doi:10.1002/ajh.25811
5. Shao, H., Wang, W., Song, J., Tang, G., Zhang, X., Tang, Z., . . . Zhang, L. (2020). Myeloid/lymphoid neoplasms with eosinophilia and FLT3 rearrangement. Leukemia Research, 99, 106460. doi:10.1016/j.leukres.2020.106460
6. Iriyama N, Takahashi H, Naruse H, Miura K, Uchino Y, Nakagawa M, Iizuka K, Hamada T, Hatta Y, Nakayama T, Takei M. A novel fusion gene involving PDGFRB and GCC2 in a chronic eosinophilic leukemia patient harboring t(2;5)(q37;q31). Mol Genet Genomic Med. 2019 Apr;7(4):e00591. doi: 10.1002/mgg3.591. Epub 2019 Jan 29. PMID: 30697976; PMCID: PMC6465652.
7. Patel AB, Franzini A, Leroy E, Kim SJ, Pomicter AD, Genet L, Xiao M, Yan D, Ahmann JM, Agarwal AM, Clair P, Addada J, Lambert J, Salmon M, Gleich GJ, Cross NCP, Constantinescu SN, O'Hare T, Prchal JT, Deininger MW. JAK2 ex13InDel drives oncogenic transformation and is associated with chronic eosinophilic leukemia and polycythemia vera. Blood. 2019 Dec 26;134(26):2388-2398. doi: 10.1182/blood.2019001385. PMID: 31697804; PMCID: PMC6933291.
8. Katalin Kelemen, MD, PhD, Leonie Saft, MD, Fiona E Craig, MD, Attilio Orazi, MD, Megan Nakashima, MD, Gerald B Wertheim, MD, PhD, Tracy I George, MD, Hans-Peter Horny, MD, Rebecca L King, MD, Leticia Quintanilla-Martinez, MD, Sa A Wang, MD, Lisa M Rimsza, MD, Kaaren K Reichard, MD, Eosinophilia/Hypereosinophilia in the Setting of Reactive and Idiopathic Causes, Well-Defined Myeloid or Lymphoid Leukemias, or Germline Disorders: Report of the 2019 Society for Hematopathology/European Association for Haematopathology Workshop, American Journal of Clinical Pathology, , aqaa244, https://doi.org/10.1093/ajcp/aqaa244

Notes

*Primary authors will typically be those that initially create and complete the content of a page.  If a subsequent user modifies the content and feels the effort put forth is of high enough significance to warrant listing in the authorship section, please contact the Associate Editor or other CCGA representative.  When pages have a major update, the new author will be acknowledged at the beginning of the page, and those who contributed previously will be acknowledged below as a prior author.

Prior Author(s):

*Citation of this Page: “Chronic eosinophilic leukaemia”. Compendium of Cancer Genome Aberrations (CCGA), Cancer Genomics Consortium (CGC), updated 11/7/2025, https://ccga.io/index.php/HAEM5:Chronic_eosinophilic_leukaemia.