STBT5:Solitary fibrous tumour

(General Instructions – The main focus of these pages is the clinically significant genetic alterations in each disease type. 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 to a table, click nearby within the table and select the > symbol that appears to be given options. 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	WHO Classification of Soft Tissue and Bone Tumours (5th Edition)
Category	Soft tissue tumours
Family	Fibroblastic and myofibroblastic tumours
Type	Solitary fibrous tumour
Subtype(s)	None

Definition / Description of Disease

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 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 paracentric inversion at chromosome 12q13q13.

Synonyms / Terminology

Formerly SFTs were categorized as hemangiopericytomas.

Epidemiology / Prevalence

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

Clinical Features

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	EXAMPLE: Cytopenias EXAMPLE: Lymphocytosis (low level)

Sites of Involvement

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.

Morphologic Features

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.

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)	CD34
Positive (universal)	STAT6 (nuclear)
Negative (universal)
Negative (subset)

Chromosomal Rearrangements (Gene Fusions)

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	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

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
EXAMPLE: 7	EXAMPLE: Loss	EXAMPLE: chr7:1-159,335,973 [hg38]	EXAMPLE: chr7	EXAMPLE: Yes	EXAMPLE: Yes	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 reference).
EXAMPLE: 8	EXAMPLE: Gain	EXAMPLE: chr8:1-145,138,636 [hg38]	EXAMPLE: chr8	EXAMPLE: No	EXAMPLE: No	EXAMPLE: No	EXAMPLE: Common recurrent secondary finding for t(8;21) (add reference).

Characteristic Chromosomal Patterns

Not Applicable

Chromosomal Pattern	Diagnostic Significance (Yes, No or Unknown)	Prognostic Significance (Yes, No or Unknown)	Therapeutic Significance (Yes, No or Unknown)	Notes
EXAMPLE: Co-deletion of 1p and 18q	EXAMPLE: Yes	EXAMPLE: No	EXAMPLE: No	EXAMPLE: See chromosomal rearrangements table as this pattern is due to an unbalanced derivative translocation associated with oligodendroglioma (add reference).

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 and common as well either disease defining and/or clinically significant. Can include references 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. Do not delete table.)

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
	EXAMPLE: TSG	EXAMPLE: 20% (COSMIC) EXAMPLE: 30% (add Reference)	EXAMPLE: IDH1 R123H	EXAMPLE: EGFR amplification	EXAMPLE: Yes	EXAMPLE: No	EXAMPLE: No	EXAMPLE: Excludes hairy cell leukemia (HCL) (add reference).

Note: A more extensive list of mutations can be found in cBioportal (https://www.cbioportal.org/), COSMIC (https://cancer.sanger.ac.uk/cosmic), ICGC (https://dcc.icgc.org/) and/or other databases. When applicable, gene-specific pages within the CCGA site directly link to pertinent external content.

Epigenomic Alterations

Not Applicable

Genes and Main Pathways Involved

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

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

Put your text here

Familial Forms

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

Additional Information

Put your text here

Links

(use the "Link" icon that looks like two overlapping circles at the top of the page) (Instructions: Highlight text to which you want to add a link in this section or elsewhere, select the "Link" icon at the top of the page, and search the name of the internal page to which you want to link this text, or enter an external internet address by including the "http://www." portion.)

References

(use the "Cite" icon at the top of the page) (Instructions: Add each reference into the text above by clicking on where you want to insert the reference, selecting the “Cite” icon at the top of the page, and using the “Automatic” tab option to search such as by PMID to select the reference to insert. The reference list in this section will be automatically generated and sorted. If a PMID is not available, such as for a book, please use the “Cite” icon, select “Manual” and then “Basic Form”, and include the entire reference.)

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.