STBT5:Solitary fibrous tumour: Difference between revisions

==Morphologic Features==

{| class="wikitable sortable"

|Negative

|Cytokeratins

* 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 small paracentric inversion at chromosome 12q13.

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

* 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.

* 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.

Positive - CD34, STAT6 (nuclear), BCL2 (30%), CD99 (70%), EMA (30%) and Actin (20%)<ref name=":5" />

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