Solitary fibrous tumour

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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)*

Reba Daniel and Shashi Shetty

WHO Classification of Disease

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

Related Terminology

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


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


Put your text here and fill in the table (Instruction: Can include references in the table. Do not delete table.)

Chromosomal Rearrangement Genes in Fusion (5’ or 3’ Segments) Pathogenic Derivative Prevalence Diagnostic Significance (Yes, No or Unknown) Prognostic Significance (Yes, No or Unknown) Therapeutic Significance (Yes, No or Unknown) Notes
inv(12)(q13q13) 3'STAT6 / 5'NAB2[1][2][3][4][5][6] NA 55-100% Yes Unknown No Many different breakpoints in the exons and introns are associated with this fusion. Ex: NAB2ex4-STAT6ex2; NAB2ex6-STAT6ex16/17


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.



Not Applicable

Chr # Gain / Loss / Amp / LOH Minimal Region Genomic Coordinates [Genome Build] Minimal Region Cytoband Diagnostic Significance (Yes, No or Unknown) Prognostic Significance (Yes, No or Unknown) Therapeutic Significance (Yes, No or Unknown) Notes


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



Not Applicable

Chromosomal Pattern Diagnostic Significance (Yes, No or Unknown) Prognostic Significance (Yes, No or Unknown) Therapeutic Significance (Yes, No or Unknown) Notes


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.


There are multiple genes with single nucleotide variations that have been reported only in metastatic solitary fibrous tumor tissues including TP53 and APAF1.[7]

Gene; Genetic Alteration Presumed Mechanism (Tumor Suppressor Gene [TSG] / Oncogene / Other) Prevalence (COSMIC / TCGA / Other) Concomitant Mutations Mutually Exclusive Mutations Diagnostic Significance (Yes, No or Unknown) Prognostic Significance (Yes, No or Unknown) Therapeutic Significance (Yes, No or Unknown) Notes
TERT Oncogene 13-29% [8][9][10][11][12] No Yes[6][8][12][13][14] No
TP53 TSG 6.3-41%[15][7] No Yes[16][15] No Single base pair substitution have been identified in exon 5 or exon 6 of TP53. [8] Mutations of TP53 have been associated with malignant and dedifferentiated SFTs.[17][18][19]
APAF1 Other 66.7% No Yes[7] No Alteration of APAF1 results in gain of a stop codon. The gene is inactivated by DNA methylation of the promoter region. Decreased APAF1 is considered to lead to inhibition of apoptosis. This alteration and decreased APAF1 mRNA expression was observed in metastatic SFT.


Epigenomic Alterations

Not Applicable

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


Gene; Genetic Alteration Pathway Pathophysiologic Outcome
NAB2::STAT6; Activating mutation EGR Pathway Increased activation of EGR1


Genetic Diagnostic Testing Methods

Ancillary studies such as immunohistochemistry and molecular tests are useful in differentiating soft tissue tumors. SFTs have historically been diagnosed by morphology and strong diffuse CD34 positivity. Additional immunohistochemical phenotype previously used for identification included expression of Bcl2, CD99, and vimentin and absence of expression of epithelial, muscle, and neural markers. However, the introduction of STAT6 (signal transducer and activator of transcription 6) immunostain now dominates due to its high sensitivity and specificity. STAT6 expression is demonstrated by nuclear staining. Next generation sequencing (NGS) using mRNA is also highly useful in detecting the NAB2::STAT6 fusion. Breakapart fluorescence in situ hybridization (FISH) probe for STAT6 can detect rearrangement of this gene.  In the context of SFT, the rearrangement of the STAT6 gene is highly suggestive for the presence of NAB2-STAT6 fusion. A dual color dual fusion probe targeting both genes would be a direct confirmation for NAB2-STAT6 fusion.

Familial Forms

Not Applicable

Additional Information

This disease is defined/characterized as detailed below:

  • Solitary fibrous tumor (SFT) is a mesenchymal spindle cell neoplasm that can develop at any site in the body, including soft tissue, visceral organs, bone, etc.  It was first described by Klemperer and Rabin[20] in 1992 as a tumor of the pleura. However, since then this entity has been increasingly described from extrapleural sites. A morphologic clue to the diagnosis is the distinctive branching “staghorn” vessels. SFT is characterized by NAB2::STAT6 fusion resulting from a small paracentric inversion at chromosome 12q13.

The epidemiology/prevalence of this disease is detailed below:

  • SFT occurs most commonly in adults with no gender predilection. Incidence of the tumor is highest in the age group of 40-70 years.

The clinical features of this disease are detailed below:

Signs and symptoms - SFTs present as slow-growing, painless neoplasms. Clinical symptoms can be due to mass effect in the site of involvement. e.g. Abdomen/Pelvis: abdominal distention, constipation, urinary retention Head/Neck: Dysphonia, nasal obstruction, dysphagia

Laboratory findings - N/A

The sites of involvement of this disease are detailed below:

  • SFTs may occur at any site of the body. Involvement of head and neck, deep soft tissues, abdominal cavity, retroperitoneum, pelvis, bone, and visceral organs have been reported.

The morphologic features of this disease are detailed below:

  • Morphologically, biopsy or resection specimens will show a bland spindle cell proliferation arranged haphazardly in a background of collagenous stroma. Cells contain ovoid nuclei within eosinophilic cytoplasm with indistinct cell borders. Tumors can vary in cellularity and stromal collagen. On low power, branching, “staghorn” shaped vessels can often be appreciated. Mitotic counts are usually low. Myxoid and lipomatous change have been described. SFT with adipocytic component are referred to as fat-forming (lipomatous) SFTs. There is also a variant known as giant cell rich SFT, which has the classic patternless spindle cell proliferation admixed with multinucleated giant cells. Dedifferentiated SFTs will show conventional SFT transitioning to a high-grade pleomorphic variant. Heterologous elements may be present. Standard immunophenotypic expression of CD34 and STAT6 is often lost in the dedifferentiated component.

The immunophenotype of this disease is detailed below:

Positive - CD34, STAT6 (nuclear), BCL2 (30%), CD99 (70%), EMA (30%) and Actin (20%)[21]

Negative - S100, Desmin and Cytokeratins[21]

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):

  1. Huang, Shih‐Chiang; et al. (2016-02). "The clinicopathological significance of NAB 2‐ STAT 6 gene fusions in 52 cases of intrathoracic solitary fibrous tumors". Cancer Medicine. 5 (2): 159–168. doi:10.1002/cam4.572. ISSN 2045-7634. Check date values in: |date= (help)
  2. Chmielecki, Juliann; et al. (2013-02). "Whole-exome sequencing identifies a recurrent NAB2-STAT6 fusion in solitary fibrous tumors". Nature Genetics. 45 (2): 131–132. doi:10.1038/ng.2522. ISSN 1061-4036. Check date values in: |date= (help)
  3. Robinson, Dan R; et al. (2013-02). "Identification of recurrent NAB2-STAT6 gene fusions in solitary fibrous tumor by integrative sequencing". Nature Genetics. 45 (2): 180–185. doi:10.1038/ng.2509. ISSN 1061-4036. Check date values in: |date= (help)
  4. Mohajeri, Arezoo; et al. (2013-10). "Comprehensive genetic analysis identifies a pathognomonic NAB2/STAT6 fusion gene, nonrandom secondary genomic imbalances, and a characteristic gene expression profile in solitary fibrous tumor". Genes, Chromosomes and Cancer. 52 (10): 873–886. doi:10.1002/gcc.22083. ISSN 1045-2257. Check date values in: |date= (help)
  5. Vogels, Rob JC; et al. (2014-12). "Solitary fibrous tumor – clinicopathologic, immunohistochemical and molecular analysis of 28 cases". Diagnostic Pathology. 9 (1). doi:10.1186/s13000-014-0224-6. ISSN 1746-1596. Check date values in: |date= (help)
  6. 6.0 6.1 Akaike, Keisuke; et al. (2015-03). "Distinct clinicopathological features of NAB2-STAT6 fusion gene variants in solitary fibrous tumor with emphasis on the acquisition of highly malignant potential". Human Pathology. 46 (3): 347–356. doi:10.1016/j.humpath.2014.11.018. Check date values in: |date= (help)
  7. 7.0 7.1 7.2 Park, Hyung Kyu; et al. (2019). "Molecular changes in solitary fibrous tumor progression". Journal of Molecular Medicine (Berlin, Germany). 97 (10): 1413–1425. doi:10.1007/s00109-019-01815-8. ISSN 0946-2716. PMC 6746689. PMID 31321477.
  8. 8.0 8.1 8.2 Bahrami, Armita; et al. (2016-12). "TERT promoter mutations and prognosis in solitary fibrous tumor". Modern Pathology. 29 (12): 1511–1522. doi:10.1038/modpathol.2016.126. Check date values in: |date= (help)
  9. Liu, Xiaoli; et al. (2013-08). "Highly prevalent TERT promoter mutations in aggressive thyroid cancers". Endocrine-Related Cancer. 20 (4): 603–610. doi:10.1530/ERC-13-0210. ISSN 1351-0088. PMC 3782569. PMID 23766237. Check date values in: |date= (help)CS1 maint: PMC format (link)
  10. Killela, Patrick J.; et al. (2013-04-09). "TERT promoter mutations occur frequently in gliomas and a subset of tumors derived from cells with low rates of self-renewal". Proceedings of the National Academy of Sciences. 110 (15): 6021–6026. doi:10.1073/pnas.1303607110. ISSN 0027-8424. PMC 3625331. PMID 23530248.CS1 maint: PMC format (link)
  11. Koelsche, Christian; et al. (2014-12). "TERT promoter hotspot mutations are recurrent in myxoid liposarcomas but rare in other soft tissue sarcoma entities". Journal of Experimental & Clinical Cancer Research. 33 (1). doi:10.1186/1756-9966-33-33. ISSN 1756-9966. Check date values in: |date= (help)
  12. 12.0 12.1 Demicco, Elizabeth G.; et al. (2018-11). "TERT promoter mutations in solitary fibrous tumour". Histopathology. 73 (5): 843–851. doi:10.1111/his.13703. ISSN 1365-2559. PMID 29985536. Check date values in: |date= (help)
  13. Park, Hyung Kyu; et al. (2019-10). "Molecular changes in solitary fibrous tumor progression". Journal of Molecular Medicine (Berlin, Germany). 97 (10): 1413–1425. doi:10.1007/s00109-019-01815-8. ISSN 1432-1440. PMC 6746689. PMID 31321477. Check date values in: |date= (help)
  14. Bahrami, Armita; et al. (2016-12). "TERT promoter mutations and prognosis in solitary fibrous tumor". Modern Pathology: An Official Journal of the United States and Canadian Academy of Pathology, Inc. 29 (12): 1511–1522. doi:10.1038/modpathol.2016.126. ISSN 1530-0285. PMC 5731237. PMID 27562490. Check date values in: |date= (help)
  15. 15.0 15.1 Yao, Chen-Chen; et al. (2023). "Prognostic analysis of extrameningeal solitary fibrous tumor using the modified Demicco model: a clinicopathologic study of 111 Chinese cases". Frontiers in Oncology. 13: 1272090. doi:10.3389/fonc.2023.1272090. ISSN 2234-943X. PMC PMC10796168 Check |pmc= value (help). PMID 38239634 Check |pmid= value (help).CS1 maint: PMC format (link)
  16. Machado, Isidro; et al. (2020-04). "Solitary fibrous tumor: a case series identifying pathological adverse factors-implications for risk stratification and classification". Virchows Archiv: An International Journal of Pathology. 476 (4): 597–607. doi:10.1007/s00428-019-02660-3. ISSN 1432-2307. PMID 31529158. Check date values in: |date= (help)
  17. Dagrada, Gian P.; et al. (2015-08). "Solitary fibrous tumors: loss of chimeric protein expression and genomic instability mark dedifferentiation". Modern Pathology: An Official Journal of the United States and Canadian Academy of Pathology, Inc. 28 (8): 1074–1083. doi:10.1038/modpathol.2015.70. ISSN 1530-0285. PMID 26022454. Check date values in: |date= (help)
  18. Kurisaki-Arakawa, Aiko; et al. (2014-11). "A case of dedifferentiated solitary fibrous tumor in the pelvis with TP53 mutation". Virchows Archiv: An International Journal of Pathology. 465 (5): 615–621. doi:10.1007/s00428-014-1625-3. ISSN 1432-2307. PMID 25015562. Check date values in: |date= (help)
  19. Nonaka, Haruna; et al. (2021). "Case Report: Molecular Characterization of Aggressive Malignant Retroperitoneal Solitary Fibrous Tumor: A Case Study". Frontiers in Oncology. 11: 736969. doi:10.3389/fonc.2021.736969. ISSN 2234-943X. PMC 8727594 Check |pmc= value (help). PMID 35004271 Check |pmid= value (help).
  20. Klemperer, Paul; et al. (1992-01). "Primary Neoplasms of the pleura. A report of five cases". American Journal of Industrial Medicine. 22 (1): 4–31. doi:10.1002/ajim.4700220103. ISSN 0271-3586. Check date values in: |date= (help)
  21. 21.0 21.1 Goldblum, John R, et al. Enzinger & Weiss’s Soft Tissue Tumors. 7th ed., Philadelphia, PA, Elsevier, 2020, pp. 1133–1147.

*Citation of this Page: “Solitary fibrous tumour”. Compendium of Cancer Genome Aberrations (CCGA), Cancer Genomics Consortium (CGC), updated 09/7/2025, https://ccga.io/index.php/STBT5:Solitary fibrous tumour.