Inflammatory myofibroblastic tumour

Soft Tissue and Bone Tumours (Who Classification, 5th ed.)

(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)*

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WHO Classification of Disease

Structure	Disease
Book	Soft Tissue and Bone Tumours (5th ed.)
Category	Soft tissue tumours
Family	Fibroblastic and myofibroblastic tumours
Type	Inflammatory myofibroblastic tumour
Subtype(s)	N/A

Related Terminology

Acceptable	N/A
Not Recommended	Plasma cell granuloma; inflammatory pseudotumour; inflammatory myofibrohistiocytic proliferation; omental-mesenteric myxoid hamartoma; inflammatory fibrosarcoma

Gene Rearrangements

Formerly referred to as inflammatory pseudotumor, inflammatory myofibroblastic tumor of the breast relies upon morphologic, immunohistochemical, and/or molecular features shared in common with other primary tumor sites. Confirmation of rearrangements of ALK or, less commonly other receptor tyrosine kinase genes, supports the diagnosis and can identify therapeutic targets. However, molecular confirmation is not required if ALK immunohistochemistry is definitively positive. Of note, exceptional situations such as inversions or other cryptic rearrangements of ALK at 2p23 may lead to a false-negative FISH result, and other molecular testing such as RNA-Seq can be used to detect ALK fusions efficiently. In ALK-negative cases, immunohistochemistry for ROS1 and/or molecular tests for non-ALK gene fusions may be useful.

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
ALK	TPM3::ALK, TPM4::ALK, EML4::ALK, RANBP2::ALK, CLTC::ALK, and others	Fusions result in constitutive activation of the ALK tyrosine kinase. The most common ALK fusion breakpoints occur in intron 19 of ALK. At the transcript level, a variable (5’) partner gene is fused to 3’ ALK at exon 20. At the DNA level, alternative ALK breakpoints in rare cases occur upstream of exon 19, most commonly in intron 18.	Rearrangements of ALK gene locus at 2p23	Common	D, T	Yes (WHO)
ROS1	TFG::ROS1, YWHAE::ROS1, and others	Fusions result in constitutive activation of the ROS1 tyrosine kinase. Most common ROS1 breakpoints occur in intron 35; at the transcript level, various 5' partner genes are fused to exon 36 of ROS1.	Rearrangements of ROS1 gene locus at 6q22	Recurrent	D, T	Yes (WHO)
NTRK3	ETV6::NTRK3 and others	Fusions result in constitutive activation of the NTRK3 tyrosine kinase. Most commonly exon 5 of ETV6 is joined to exon 15 of NTRK3 at the transcript level.	Rearrangements of NTRK3 gene locus at 15q25. Classically, the reciprocal translocation t(12;15)(p13;q25) is associated with ETV6::NTRK3 rearrangement.	Recurrent	D, T	Yes (WHO)
PDGFRB	NAB2::PDGFRB and others	Fusions result in constitutive activation of the PDGFRB tyrosine kinase.	Rearrangements of the PDGFRB gene locus at 5q32.	Rare	D, T	Yes (WHO)
RET		Fusions result in constitutive activation of the RET tyrosine kinase.	Rearrangements of the RET gene locus at 10q11.	Rare	D, T	Yes (WHO)
NTRK1		Fusions result in constitutive activation of the NTRK1 tyrosine kinase.	Rearrangements of the NTRK1 gene locus at 1q23.	Rare	D, T
IGF1R		Fusions result in constitutive activation of the IGF1R tyrosine kinase.	Rearrangements of the IGF1R gene locus at 15q26.	Rare	D, T

Individual Region Genomic Gain/Loss/LOH

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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.

Characteristic Chromosomal or Other Global Mutational Patterns

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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

Gene Mutations (SNV/INDEL)

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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.

Epigenomic Alterations

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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

Genetic Diagnostic Testing Methods

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Familial Forms

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Additional Information

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Links

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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 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: “Inflammatory myofibroblastic tumour”. Compendium of Cancer Genome Aberrations (CCGA), Cancer Genomics Consortium (CGC), updated 02/12/2026, https://ccga.io/index.php/STBT5:Inflammatory myofibroblastic tumour.