HAEM5:B lymphoblastic leukaemia/lymphoma with TCF3::PBX1 fusion

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:B-Lymphoblastic Leukemia/Lymphoma with t(1;19)(q23;p13.3); TCF3-PBX1.

(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)*

Miguel Gonzalez Mancera, MD

WHO Classification of Disease

Structure	Disease
Book	Haematolymphoid Tumours (5th ed.)
Category	B-cell lymphoid proliferations and lymphomas
Family	Precursor B-cell neoplasms
Type	B-lymphoblastic leukaemias/lymphomas
Subtype(s)	B lymphoblastic leukaemia/lymphoma with TCF3::PBX1 fusion

Related Terminology

Acceptable	N/A
Not Recommended	B-lymphoblastic leukaemia/lymphoma with E2A::PBX1

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
TCF3::PBX1 fusion protein	TCF3::PBX1	The TCF3::PBX1 fusion results in the production of a fusion protein that has an oncogenic role as a transcriptional activator; it also probably interferes with the normal function of the transcription factors encoded by TCF3 and PBX1. Oligomerization and/or direct interaction with HOX proteins through the PBX1 moiety may play a role in TCF3-PBX1 leukemogenesis.	t(1;19)(q23;q13.3)	Common	D: Requires demonstration of TCF3::PBX1 rearrangement P: Associated with intermediate to relatively favorable clinical outcomes T: N/A	No (NCCN)	There may be an increased relative risk of CNS relapse in these patients. Relapsed patients appear to have a dismal prognosis. Although the t(1;19) translocation can be readily detected by conventional chromosome studies, FISH confirmation is often needed since a karyotypically similar t(1;19) without involvement of TCF3 or PBX1 has been reported.

editv4:Chromosomal Rearrangements (Gene Fusions)

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The breakpoints of the t(1;19) translocation typically fall within intron 16 of TCF3 and intron 3 of PBX1.

Chromosomal Rearrangement	Genes in Fusion (5’ or 3’ Segments)	Pathogenic Derivative	Prevalence
t(1;19)(q23;p13.3)	TCF3-PBX1	der(19)	More common (75%)
t(1;19)(q23;p13.3)	TCF3-PBX1	Balanced translocation	Less common

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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)

The t(1;19) diagnosis was associated with high risk and poor prognosis in earlier studies, however, modern intensive chemotherapy has changed this paradigm. A recent (2021) study showed that patients with TCF3-PBX1 had intermediate rates of 5-year event-free survival (80-88.2%). Despite the favorable prognosis of this subtype of ALL, there is an increased relative risk of central nervous system relapse associated with this translocation.

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Individual Region Genomic Gain/Loss/LOH

Secondary somatic copy number aberrations are not frequently seen in TCF3-PBX1 B-ALL. 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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Secondary somatic copy number aberrations are not frequently seen in TCF3-PBX1 B-ALL

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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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The t(1;19) translocation can be balanced or unbalanced. The unbalanced form has a der(19) resulting in trisomy of 1q distal to PBX1.

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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
PHF6	EXAMPLE: Exon 18-21 activating mutations	Transcription factor	Recurrent	D: N/A T: N/A T: N/A	No (NCCN)
PAX5	EXAMPLE: Variable LOF mutations	Transcription factor	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.

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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Secondary somatic DNA mutations are not frequently seen in TCF3-PBX1 B-ALL.

Other Mutations

Secondary somatic copy number aberrations and DNA mutations are not frequently seen in TCF3-PBX1 B-ALL, commonly found additional abnormalities are listed below.

Type	Gene/Region/Other
Additional abnormalities	dup(1q), del(6q), +8, i(9q), i(17q), +21

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Epigenomic Alterations

Put your text here

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
	WNT signaling	Increased cell-proliferation, survival and chemotaxis

editv4:Genes and Main Pathways Involved

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TCF3 gene at 19p13.3 is important during early lymphocyte development, whereas PBX1 at 1q23 is a component of a transcriptional complex that regulates embryogenesis and hematopoiesis. Fusion protein resulting from the TCF3-PBX1 translocation is a transcriptional activator which likely interferes with the normal function of these genes. Expression of this fusion protein is thought to interfere with key regulatory pathways such as WNT and apoptosis/cell cycle control pathways which may drive a leukemic process. The DNA-binding and protein dimerization domains of PBX1 replaces the TCF3 helix-loop-helix DNA-binding motif in TCF3-PBX1 fusion. The remaining transcriptional activating domains of TCF3 leads to constitutive nuclear localization and transformation of PBX1 into an oncogenic transcriptional factor

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Genetic Diagnostic Testing Methods

• Conventional chromosome analysis with FISH confirmation

• RT-PCR
• DNA or RNA based NGS analysis

Familial Forms

Put your text here (Instructions: Include associated hereditary conditions/syndromes that cause this entity or are caused by this entity.)

Additional Information

• Another translocation involving the TCF3 gene is t(17;19) which results in the fusion of HLF at 17q22 with TCF3. This variant translocation has been reported in approximately 1% of pediatric B-ALL patients and is associated with a poor prognosis.
• A karyotypically identical t(1;19) has been observed in a subset of B-ALL cases, especially in hyperdiploid B-ALL. This translocation does not involve TCF3 or PBX1. Therefore, a FISH confirmation is often necessary to determine the nature of t(1;19).

Links

TCF3

PBX1

Put your links here (use "Link" icon at top of page)

References

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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 CCGA coordinators (contact information provided on the homepage). Additional global feedback or concerns are also welcome.

*Citation of this Page: “B lymphoblastic leukaemia/lymphoma with TCF3::PBX1 fusion”. Compendium of Cancer Genome Aberrations (CCGA), Cancer Genomics Consortium (CGC), updated 11/10/2025, https://ccga.io/index.php/HAEM5:B_lymphoblastic_leukaemia/lymphoma_with_TCF3::PBX1_fusion.