Changes

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==Definition / Description of Disease==

==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.  

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<ref>{{Cite journal|last=Klemperer|first=Paul|last2=Rabin|first2=Coleman B.|date=1992-01|title=Primary Neoplasms of the pleura. A report of five cases|url=https://onlinelibrary.wiley.com/doi/10.1002/ajim.4700220103|journal=American Journal of Industrial Medicine|language=en|volume=22|issue=1|pages=4–31|doi=10.1002/ajim.4700220103|issn=0271-3586}}</ref> 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==

==Synonyms / Terminology==

Formerly SFTs were categorized as hemangiopericytomas.  

Formerly SFTs were categorized as hemangiopericytomas.  

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|'''Laboratory Findings'''

|'''Laboratory Findings'''

|<span class="blue-text">EXAMPLE:</span> Cytopenias

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==Sites of Involvement==

==Sites of Involvement==

==Morphologic Features==

==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.  

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==

==Immunophenotype<ref>Goldblum, John R, et al. ''Enzinger & Weiss’s Soft Tissue Tumors''. 7th ed., Philadelphia, PA, Elsevier, 2020, pp. 1133–1147.</ref>==

Put your text here and fill in the table <span style="color:#0070C0">(''Instruction: Can include references in the table. Do not delete table.'') </span>

Put your text here and fill in the table <span style="color:#0070C0">(''Instruction: Can include references in the table. Do not delete table.'') </span>

{| class="wikitable sortable"

{| class="wikitable sortable"

!Finding!!Marker

!Finding!!Marker

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|Positive (universal)||CD34

|Positive||CD34

|EMA (30%)

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|Positive

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|Positive (universal)||STAT6 (nuclear)

|Negative

|S100

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|Negative (universal)||

|Negative

|Desmin

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|Negative (subset)||

|Negative

|Cytokeratins

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==Chromosomal Rearrangements (Gene Fusions)==

==Chromosomal Rearrangements (Gene Fusions)==

!Notes

!Notes

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|inv(12)(q13q13)||3'STAT6 / 5'NAB2||NA||55-100%

|inv(12)(q13q13)||3'STAT6 / 5'NAB2<ref>{{Cite journal|last=Huang|first=Shih‐Chiang|last2=Li|first2=Chien‐Feng|last3=Kao|first3=Yu‐Chien|last4=Chuang|first4=I‐Chieh|last5=Tai|first5=Hui‐Chun|last6=Tsai|first6=Jen‐Wei|last7=Yu|first7=Shih‐Chen|last8=Huang|first8=Hsuan‐Ying|last9=Lan|first9=Jui|date=2016-02|title=The clinicopathological significance of  NAB 2‐ STAT 6  gene fusions in 52 cases of intrathoracic solitary fibrous tumors|url=https://onlinelibrary.wiley.com/doi/10.1002/cam4.572|journal=Cancer Medicine|language=en|volume=5|issue=2|pages=159–168|doi=10.1002/cam4.572|issn=2045-7634}}</ref><ref>{{Cite journal|last=Chmielecki|first=Juliann|last2=Crago|first2=Aimee M|last3=Rosenberg|first3=Mara|last4=O'Connor|first4=Rachael|last5=Walker|first5=Sarah R|last6=Ambrogio|first6=Lauren|last7=Auclair|first7=Daniel|last8=McKenna|first8=Aaron|last9=Heinrich|first9=Michael C|date=2013-02|title=Whole-exome sequencing identifies a recurrent NAB2-STAT6 fusion in solitary fibrous tumors|url=https://www.nature.com/articles/ng.2522|journal=Nature Genetics|language=en|volume=45|issue=2|pages=131–132|doi=10.1038/ng.2522|issn=1061-4036}}</ref><ref>{{Cite journal|last=Robinson|first=Dan R|last2=Wu|first2=Yi-Mi|last3=Kalyana-Sundaram|first3=Shanker|last4=Cao|first4=Xuhong|last5=Lonigro|first5=Robert J|last6=Sung|first6=Yun-Shao|last7=Chen|first7=Chun-Liang|last8=Zhang|first8=Lei|last9=Wang|first9=Rui|date=2013-02|title=Identification of recurrent NAB2-STAT6 gene fusions in solitary fibrous tumor by integrative sequencing|url=https://www.nature.com/articles/ng.2509|journal=Nature Genetics|language=en|volume=45|issue=2|pages=180–185|doi=10.1038/ng.2509|issn=1061-4036}}</ref><ref>{{Cite journal|last=Mohajeri|first=Arezoo|last2=Tayebwa|first2=Johnbosco|last3=Collin|first3=Anna|last4=Nilsson|first4=Jenny|last5=Magnusson|first5=Linda|last6=von Steyern|first6=Fredrik Vult|last7=Brosjö|first7=Otte|last8=Domanski|first8=Henryk A.|last9=Larsson|first9=Olle|date=2013-10|title=Comprehensive genetic analysis identifies a pathognomonic NAB2/STAT6 fusion gene, nonrandom secondary genomic imbalances, and a characteristic gene expression profile in solitary fibrous tumor|url=https://onlinelibrary.wiley.com/doi/10.1002/gcc.22083|journal=Genes, Chromosomes and Cancer|language=en|volume=52|issue=10|pages=873–886|doi=10.1002/gcc.22083|issn=1045-2257}}</ref><ref>{{Cite journal|last=Vogels|first=Rob JC|last2=Vlenterie|first2=Myrella|last3=Versleijen-Jonkers|first3=Yvonne MH|last4=Ruijter|first4=Emiel|last5=Bekers|first5=Elise M|last6=Verdijk|first6=Marian AJ|last7=Link|first7=Monique M|last8=Bonenkamp|first8=Johannes J|last9=van der Graaf|first9=Winette TA|date=2014-12|title=Solitary fibrous tumor – clinicopathologic, immunohistochemical and molecular analysis of 28 cases|url=https://diagnosticpathology.biomedcentral.com/articles/10.1186/s13000-014-0224-6|journal=Diagnostic Pathology|language=en|volume=9|issue=1|doi=10.1186/s13000-014-0224-6|issn=1746-1596}}</ref><ref name=":0">{{Cite journal|last=Akaike|first=Keisuke|last2=Kurisaki-Arakawa|first2=Aiko|last3=Hara|first3=Kieko|last4=Suehara|first4=Yoshiyuki|last5=Takagi|first5=Tatsuya|last6=Mitani|first6=Keiko|last7=Kaneko|first7=Kazuo|last8=Yao|first8=Takashi|last9=Saito|first9=Tsuyoshi|date=2015-03|title=Distinct clinicopathological features of NAB2-STAT6 fusion gene variants in solitary fibrous tumor with emphasis on the acquisition of highly malignant potential|url=https://linkinghub.elsevier.com/retrieve/pii/S0046817714004912|journal=Human Pathology|language=en|volume=46|issue=3|pages=347–356|doi=10.1016/j.humpath.2014.11.018}}</ref>||NA||55-100%

|Yes

|Yes

|Unknown

|Unknown

!Notes

!Notes

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|<span class="blue-text">EXAMPLE:</span>

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|<span class="blue-text">EXAMPLE:</span> Loss

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|<span class="blue-text">EXAMPLE:</span>

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|<span class="blue-text">EXAMPLE:</span>

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|<span class="blue-text">EXAMPLE:</span> Yes

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|<span class="blue-text">EXAMPLE:</span> Yes

|<span class="blue-text">EXAMPLE:</span> No

|<span class="blue-text">EXAMPLE:</span>

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|<span class="blue-text">EXAMPLE:</span>

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|<span class="blue-text">EXAMPLE:</span> Gain

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|<span class="blue-text">EXAMPLE:</span>

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|<span class="blue-text">EXAMPLE:</span>

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|<span class="blue-text">EXAMPLE:</span> No

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|<span class="blue-text">EXAMPLE:</span> No

|<span class="blue-text">EXAMPLE:</span> No

|<span class="blue-text">EXAMPLE:</span>

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==Characteristic Chromosomal Patterns==

==Characteristic Chromosomal Patterns==

Not Applicable

Not Applicable

!Notes

!Notes

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|<span class="blue-text">EXAMPLE:</span>

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|<span class="blue-text">EXAMPLE:</span> Yes

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|<span class="blue-text">EXAMPLE:</span> No

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|<span class="blue-text">EXAMPLE:</span> No

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|<span class="blue-text">EXAMPLE:</span>

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==Gene Mutations (SNV / INDEL)==

==Gene Mutations (SNV / INDEL)==

Put your text here and fill in the table <span style="color:#0070C0">(''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.'') </span>

There are multiple genes with single nucleotide variations that have been reported only in metastatic solitary fibrous tumor tissues including TP53 and APAF1.<ref name=":1">{{Cite journal|last=Park|first=Hyung Kyu|last2=Yu|first2=Dan Bi|last3=Sung|first3=Minjung|last4=Oh|first4=Ensel|last5=Kim|first5=Mingi|last6=Song|first6=Ji-Young|last7=Lee|first7=Mi-Sook|last8=Jung|first8=Kyungsoo|last9=Noh|first9=Ka-Won|date=2019|title=Molecular changes in solitary fibrous tumor progression|url=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6746689/|journal=Journal of Molecular Medicine (Berlin, Germany)|volume=97|issue=10|pages=1413–1425|doi=10.1007/s00109-019-01815-8|issn=0946-2716|pmc=6746689|pmid=31321477}}</ref>  

{| class="wikitable sortable"

{| class="wikitable sortable"

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!Notes

!Notes

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|<span class="blue-text">EXAMPLE:</span> TSG

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|<span class="blue-text">EXAMPLE:</span> 20% (COSMIC)

|No

|Yes<ref name=":1" />

|<span class="blue-text">EXAMPLE:</span> ''IDH1'' R123H

|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.

|<span class="blue-text">EXAMPLE:</span> Yes

|<span class="blue-text">EXAMPLE:</span> No

|<span class="blue-text">EXAMPLE:</span> No

|<span class="blue-text">EXAMPLE:</span> 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==

==Epigenomic Alterations==

Not Applicable

Not Applicable

==Genes and Main Pathways Involved==

==Genes and Main Pathways Involved==

{| class="wikitable sortable"

{| class="wikitable sortable"

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|EGR Pathway

|EGR Pathway

|Increased activation of EGR1

|Increased activation of EGR1

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==Genetic Diagnostic Testing Methods==

==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. Molecular testing by next generation sequencing 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. [https://pubmed.ncbi.nlm.nih.gov/27802414/ A dual color dual fusion probe targeting both genes would be a direct confirmation for ''NAB2-STAT6'' fusion.]

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. [https://pubmed.ncbi.nlm.nih.gov/27802414/ A dual color dual fusion probe targeting both genes would be a direct confirmation for ''NAB2-STAT6'' fusion.]

==Familial Forms==

==Familial Forms==

Not Applicable

Not Applicable

==Notes==

==Notes==

<nowiki>*</nowiki>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.

<nowiki>*</nowiki>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.