Acute undifferentiated leukaemia
Haematolymphoid Tumours (WHO Classification, 5th ed.)
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editContent Update To WHO 5th Edition Classification Is In Process; Content Below is Based on WHO 4th Edition ClassificationThis page was converted to the new template on 2023-12-07. The original page can be found at HAEM4:Acute Undifferentiated Leukemia.
(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)*
Amelia Nakanishi, MD and Shashi Shetty, PhD
WHO Classification of Disease
| Structure | Disease |
|---|---|
| Book | Haematolymphoid Tumours (5th ed.) |
| Category | Myeloid proliferations and neoplasms |
| Family | Acute leukaemias of mixed or ambiguous lineage |
| Type | Acute leukaemia of ambiguous lineage, immunophenotypically defined |
| Subtype(s) | Acute undifferentiated leukaemia |
Definition / Description of Disease
An acute leukemia with blasts that are immunophenotypically ambiguous for any one hematopoietic lineage. AUL is a diagnosis of exclusion that is incompatible with the presence of features that meet the criteria for inclusion in any of the other AML groups (i.e. AML with Recurrent Genetic Abnormalities, AML with Myelodysplasia-Related Changes, or Therapy-Related Myeloid Neoplasms).
To support an undifferentiated phenotype, AUL requires an immunophenotypic work up that “excludes unusual lineages such as plasmacytoid dendritic cell precursors, natural killer precursors, basophils, and non-hematologic cells”[1].
Synonyms / Terminology
Blast cell leukemia, stem cell leukemia, stem cell acute leukemia, undifferentiated leukemia.
Epidemiology / Prevalence
Very rare; precise frequency unknown.
Clinical Features
Put your text here and fill in the table (Instruction: Can include references in the table. Do not delete table.)
| Signs and Symptoms | EXAMPLE: Asymptomatic (incidental finding on complete blood counts)
EXAMPLE: B-symptoms (weight loss, fever, night sweats) EXAMPLE: Fatigue EXAMPLE: Lymphadenopathy (uncommon) |
| Laboratory Findings | EXAMPLE: Cytopenias
EXAMPLE: Lymphocytosis (low level) |
editv4:Clinical FeaturesThe content below was from the old template. Please incorporate above.
In one study of 16 cases of adults with AUL, the median age was 63 years (range: 24-84 years) and patients could achieve clinical remission after allogeneic stem cell transplantation[2]. In previous studies that weakly suggest ALL induction regimens over AML induction regimens, there may be selection bias in the patients who were well enough to be transplant candidates[3].
In children, based on limited clinical information in the literature, AUL has been associated with a poor prognosis[4].
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Sites of Involvement
Bone marrow and peripheral blood. AUL is so rare, it is unknown if there is a pattern of other sites of involvement.
Morphologic Features
AUL blast morphology is bland and non-specific. Cytoplasmic granulation and disease defining morphology are absent.
Immunophenotype
Put your text here and fill in the table (Instruction: Can include references in the table. Do not delete table.)
| Finding | Marker |
|---|---|
| Positive (universal) | EXAMPLE: CD1 |
| Positive (subset) | EXAMPLE: CD2 |
| Negative (universal) | EXAMPLE: CD3 |
| Negative (subset) | EXAMPLE: CD4 |
editv4:ImmunophenotypeThe content below was from the old template. Please incorporate above.
Per WHO 2017, AUL blasts should express no more than one membrane marker for any lineage.
| Positive (universal) | Precursor stage: HLA-DR, CD34, and/or CD38, CD117, CD133 [5] |
| Positive (subset) | TdT
CD7 (weak positivity) see below. |
| Negative (universal) | Myeloid: MPO
Monocytic: NSE, CD11c, Cd14, CD64, lysozyme, Cd4, CD11b, CD36, NG2 homologue T cell: cCD3 B cell: cCD22, cCD79a, strong CD19 Megakaryocytic: CD41, CD61, CD42, CD235a |
| Negative (subset) | NA |
Additional Description: Blasts are generally positive for HLA-DR, CD34, and/or CD38.
-CD7 positivity is associated with T cells, but can also be seen in some CD34+ hematopoietic stem cells and is not unexpected in a stem cell leukemia[1].
-See HAEM4:Acute Leukemias of Ambiguous Lineage for assigning lineage assignment.
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WHO Essential and Desirable Genetic Diagnostic Criteria
(Instructions: The table will have the diagnostic criteria from the WHO book autocompleted; remove any non-genetics related criteria. If applicable, add text about other classification systems that define this entity and specify how the genetics-related criteria differ.)
| WHO Essential Criteria (Genetics)* | |
| WHO Desirable Criteria (Genetics)* | |
| Other Classification |
*Note: These are only the genetic/genomic criteria. Additional diagnostic criteria can be found in the WHO Classification of Tumours.
Related Terminology
(Instructions: The table will have the related terminology from the WHO autocompleted.)
| Acceptable | |
| Not Recommended |
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
|
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)The content below was from the old template. Please incorporate above.
NA
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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)
There is evidence that the genes associated with poor prognosis in acute leukemias, BAALC, ERG, and MN1, are also overexpressed in AUL[1].
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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/LOHThe content below was from the old template. Please incorporate above.
NA
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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 / PatternsThe content below was from the old template. Please incorporate above.
AUL is associated with a high rate of chromosomal abnormalities, but have no characteristic abnormalities[2].
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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)The content below was from the old template. Please incorporate above.
PHF6 a tumor suppressor gene may have implications in AUL though the evidence is limited.
Other Mutations
NA
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Epigenomic Alterations
Unknown
Genes and Main Pathways Involved
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| 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 InvolvedThe content below was from the old template. Please incorporate above.
Overexpression of BAALC, ERG, and MN1[1].
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Genetic Diagnostic Testing Methods
Morphology, immunohistochemistry, cytochemistry, flow cytometry, cytogenetics, and next generation sequencing.
Familial Forms
Unknown
Additional Information
Although AUL and AML with minimal differentiation are both rare diagnoses, they have similar patient demographics and clinical courses. AUL and AML with minimal differentiation have different molecular abnormalities[2].
Links
References
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- ↑ 1.0 1.1 1.2 1.3 Borowitz MJ, et al., (2017). Acute leukaemias of ambiguous lineage, 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, p182.
- ↑ 2.0 2.1 2.2 Heesch, Sandra; et al. (2013). "Acute leukemias of ambiguous lineage in adults: molecular and clinical characterization". Annals of Hematology. 92 (6): 747–758. doi:10.1007/s00277-013-1694-4. ISSN 1432-0584. PMID 23412561.
- ↑ Weinberg, Olga K.; et al. (2019). "Clinical, immunophenotypic, and genomic findings of acute undifferentiated leukemia and comparison to acute myeloid leukemia with minimal differentiation: a study from the bone marrow pathology group". Modern Pathology: An Official Journal of the United States and Canadian Academy of Pathology, Inc. 32 (9): 1373–1385. doi:10.1038/s41379-019-0263-3. ISSN 1530-0285. PMID 31000771.
- ↑ Lee, Hyun Gyung; et al. (2019). "Biphenotypic acute leukemia or acute leukemia of ambiguous lineage in childhood: clinical characteristics and outcome". Blood Research. 54 (1): 63–73. doi:10.5045/br.2019.54.1.63. ISSN 2287-979X. PMC 6439300. PMID 30956966.
- ↑ Hoffman R, et al., (2018) Hematology, basic principles and practice, 7th edition. Elsevier: Philadelphia. (clinical key excerpt)
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: “Acute undifferentiated leukaemia”. Compendium of Cancer Genome Aberrations (CCGA), Cancer Genomics Consortium (CGC), updated 02/10/2025, https://ccga.io/index.php/HAEM5:Acute_undifferentiated_leukaemia.