Skip to content
Inciteful Med

What is Solitary Fibrous Tumor (SFT)?

Last updated:

Solitary Fibrous Tumor (SFT) is a rare soft tissue sarcoma driven by the NAB2-STAT6 gene fusion. Formerly known as Hemangiopericytoma, it is diagnosed via STAT6 testing. While often treatable with surgery, SFT requires long-term monitoring due to its unpredictable potential to return.

Key Takeaways

  • • SFT and Hemangiopericytoma are the same condition caused by the NAB2-STAT6 gene fusion.
  • • The presence of the STAT6 protein is the definitive diagnostic marker for this tumor.
  • • SFTs can occur anywhere but are most common in the pleura (lung lining) and meninges (brain covering).
  • • Doctors use risk models like Demicco to predict the tumor's behavior based on size and cell activity.
  • • Long-term surveillance is necessary because SFTs can recur even years after removal.

Being diagnosed with a Solitary Fibrous Tumor (SFT) can be confusing, especially because these tumors behave differently than many other types of cancer. Understanding the basics of what they are and how they grow is the first step in managing your care.

One Disease, Two Names

In the past, doctors used two different names—Solitary Fibrous Tumor (SFT) and Hemangiopericytoma (HPC)—to describe what appeared to be different types of growths [1]. However, modern medicine has discovered that these are actually the same disease [2][3].

Recent World Health Organization (WHO) classifications have unified them because they share the exact same genetic driver [4]. While you may still see the term “HPC” in older medical records or for tumors in the brain and spine, the medical community now generally uses the term SFT to cover the entire spectrum of this disease [5][6].

What is SFT?

SFT is a type of Soft Tissue Sarcoma. Sarcomas are cancers that arise from the body’s connective tissues rather than organs like the lung or breast [7]. Specifically, SFT starts in mesenchymal cells—think of these as the cells that make up the “scaffolding” or “glue” of the body, such as the tissue surrounding muscles, nerves, and blood vessels [7].

The Genetic ‘Engine’: NAB2-STAT6

The defining feature of almost every SFT is a specific genetic mistake called a fusion gene [8]. In these tumors, two pieces of DNA that normally live apart—NAB2 and STAT6—get stuck together [9][10].

Think of this NAB2-STAT6 fusion as the “engine” that drives the tumor to grow.

  • The Switch: This fusion turns a normal gene (NAB2) into an “on switch” for cell growth [8].
  • The Marker: Doctors can test for this “engine” by looking for the STAT6 protein in the nucleus (center) of the tumor cells [11]. If the test is positive, it strongly confirms that the tumor is an SFT [12][2].

Where Do They Grow?

Although SFTs were first discovered in the lining of the lungs (the pleura), they are not just “lung tumors” [13]. They can appear almost anywhere in the body. Common locations include:

  • The Pleura: About 80% of cases start in the chest cavity [13].
  • The Meninges: The protective layers surrounding the brain and spinal cord. In the brain, SFTs are often initially mistaken for Meningiomas [14].
  • Soft Tissues: Areas like the abdomen (retroperitoneum), pelvis, head, neck, and limbs [14][15].

Understanding ‘Malignant Potential’

SFT is officially classified as having intermediate biological behavior [16]. This phrasing can be confusing. It does not mean the tumor is benign or “safe.” It means SFT exists on a spectrum:

  • Unpredictability: Most SFTs grow slowly and are cured by surgery, but they are unpredictable [16]. Even a tumor that looks “tame” under a microscope can sometimes return or spread many years later [17][18].
  • Risk Factors: To predict how a tumor will behave, doctors use risk stratification models (like the Demicco system) [19]. They look at your age, the size of the tumor, how fast the cells are dividing (mitotic count), and whether there are areas of cell death (necrosis) [20][21].
  • Long-Term Monitoring: Because of this intermediate nature, doctors require long-term follow-up—often for a decade or more—to ensure that if the tumor does return, it is caught early [22][23].

Frequently Asked Questions

What is the difference between SFT and Hemangiopericytoma?
SFT and Hemangiopericytoma (HPC) are now considered the same disease. World Health Organization classifications unified them because they share the exact same genetic driver, the NAB2-STAT6 fusion gene. You may still see "HPC" used for tumors in the brain or spine.
What does a positive STAT6 test mean?
A positive STAT6 result means a specific protein was found in the nucleus of your tumor cells. This is the hallmark diagnostic marker that confirms the tumor is a Solitary Fibrous Tumor and distinguishes it from other types of growths.
What causes Solitary Fibrous Tumor?
SFT is caused by a specific genetic mistake called a "fusion gene." Two pieces of DNA—NAB2 and STAT6—get stuck together, acting as an engine that drives the tumor cells to grow.
Is Solitary Fibrous Tumor benign or cancerous?
SFT is classified as having "intermediate biological behavior." This means that while many tumors grow slowly and are cured by surgery, they can be unpredictable. Some may return or spread years later, requiring long-term monitoring.
How do doctors predict if an SFT will come back?
Doctors use risk stratification models, such as the Demicco system, to predict behavior. They analyze factors like your age, the tumor's size, the mitotic count (cell division speed), and the presence of necrosis (cell death).

Questions for Your Doctor

  • • Did my pathology report show nuclear STAT6 expression, and does this confirm the NAB2-STAT6 fusion?
  • • Is my tumor considered a 'Soft Tissue Sarcoma'?
  • • What was my tumor's mitotic count and were there any signs of necrosis (cell death)?
  • • Based on the size, age, and pathology, what is my Demicco risk score (low, intermediate, or high)?
  • • How does the location of my tumor—whether in the pleura, the brain/spine, or elsewhere—affect my prognosis?
  • • What is the plan for long-term surveillance, and how often will I need imaging like CT or MRI scans?

Questions for You

  • • What symptoms first led to your diagnosis, and have you noticed any new or changing symptoms since then?
  • • Have you experienced any unexplained episodes of low blood sugar (dizziness, shakiness, or sweating), which can sometimes be associated with these tumors?
  • • Where exactly was your tumor found, and was the surgeon able to remove it completely?
  • • How do you feel about the 'unpredictable' nature of this diagnosis, and what kind of support do you need for long-term monitoring?

Want personalized information?

Type your question below to get evidence-based answers tailored to your situation.

References

  1. 1

    Rare Occurrence of an Intraocular Choroidal Solitary Fibrous Tumor/Hemangiopericytoma.

    Rinaldo L, Xu SCY, Eggers SD, et al.

    Ocular oncology and pathology 2018; (4(4)):213-219 doi:10.1159/000481947.

    PMID: 30643764
  2. 2

    [Solitary fibrous tumor/hemangiopericytoma].

    Teranishi Y, Hongou H, Miyawaki S, Saito N

    No shinkei geka. Neurological surgery 2022; (50(1)):141-149 doi:10.11477/mf.1436204539.

    PMID: 35169094
  3. 3

    The 2020 WHO Classification: What's New in Soft Tissue Tumor Pathology?

    Kallen ME, Hornick JL

    The American journal of surgical pathology 2021; (45(1)):e1-e23 doi:10.1097/PAS.0000000000001552.

    PMID: 32796172
  4. 4

    Recurrence of Solitary Fibrous Tumor/Hemangiopericytoma Could Be Predicted by Ki-67 Regardless of Its Origin.

    Yamamoto Y, Hayashi Y, Murakami I

    Acta medica Okayama 2020; (74(4)):335-343 doi:10.18926/AMO/60372.

    PMID: 32843765
  5. 5

    Primary Intracranial Solitary Fibrous Tumor With Metachronous Pulmonary and Bone Metastasis: A Case Report.

    Alabssi H, Alismail M, Taha MS, et al.

    Cureus 2022; (14(12)):e32607 doi:10.7759/cureus.32607.

    PMID: 36654576
  6. 6

    Parotid Gland Solitary Fibrous Tumor Presenting as a Long Duration Mass: A Case Report.

    Abdulhaleem K, Dababo MA, Othman E

    Case reports in pathology 2022; (2022()):2097634 doi:10.1155/2022/2097634.

    PMID: 35251728
  7. 7

    Solitary fibrous tumor occurring in the colon as submucosal mesenchymal lesion: report of two cases and review of the literature.

    Akrmah M, Ibrahim E, Mnayer LO, Ligato S

    Clinical journal of gastroenterology 2024; (17(3)):396-400 doi:10.1007/s12328-024-01936-9.

    PMID: 38472638
  8. 8

    Advances in the molecular biology of the solitary fibrous tumor and potential impact on clinical applications.

    Ren C, D'Amato G, Hornicek FJ, et al.

    Cancer metastasis reviews 2024; (43(4)):1337-1352 doi:10.1007/s10555-024-10204-8.

    PMID: 39120790
  9. 9

    Solitary fibrous tumor: An evolving and unifying entity with unsettled issues.

    Huang SC, Huang HY

    Histology and histopathology 2019; (34(4)):313-334 doi:10.14670/HH-18-064.

    PMID: 30431144
  10. 10

    Solitary Fibrous Tumor of the Vulva: Report of 2 Cases, Including a De Novo Dedifferentiated Solitary Fibrous Tumor Diagnosed After Molecular Demonstration of NAB2-STAT6 Gene Fusion.

    Tardío JC, Machado I, Alemany I, et al.

    International journal of gynecological pathology : official journal of the International Society of Gynecological Pathologists 2018; (37(6)):547-553 doi:10.1097/PGP.0000000000000464.

    PMID: 28968297
  11. 11

    STAT6 Expression in Solitary Fibrous Tumor and Histologic Mimics: a Single Institution Experience.

    Saeed O, Zhang S, Cheng L, et al.

    Applied immunohistochemistry & molecular morphology : AIMM 2020; (28(4)):311-315 doi:10.1097/PAI.0000000000000745.

    PMID: 30664532
  12. 12

    Solitary Fibrous Tumor of the Vulva: Case Report of a Rare Entity and Review of Literature.

    Tandon N

    International journal of gynecological pathology : official journal of the International Society of Gynecological Pathologists 2021; (40(3)):234-239 doi:10.1097/PGP.0000000000000707.

    PMID: 32925444
  13. 13

    An unusual location of solitary fibrous tumor in heart-A case report and review of literature.

    Fain K, Parmar K, Sharma M, et al.

    Cancer reports (Hoboken, N.J.) 2022; (5(11)):e1698 doi:10.1002/cnr2.1698.

    PMID: 36041816
  14. 14

    Role of Immunohistochemistry in the Diagnosis of Solitary Fibrous Tumor, a Review.

    Geramizadeh B, Marzban M, Churg A

    Iranian journal of pathology 2016; (11(3)):195-203.

    PMID: 27799967
  15. 15

    Solitary fibrous tumor of the orbital region: report of a case with emphasis on the diagnostic utility of STAT-6.

    Broggi G, Salvatorelli L, Reibaldi M, et al.

    Pathologica 2020; (112(4)):195-199 doi:10.32074/1591-951X-9-20.

    PMID: 33393522
  16. 16

    Acute urinary retention due to solitary fibrous tumor of the abdominal wall.

    Fernández-Sanmillán D, De Melo Santos DM, Fernandez EL, Hernandez JRH

    Turkish journal of urology 2019; (45(6)):471-473 doi:10.5152/tud.2018.23255.

    PMID: 31603423
  17. 17

    Adrenal solitary fibrous tumor: A case report.

    Yonli DS, Chakroun M, Mokadem S, et al.

    Urology case reports 2019; (27()):100919 doi:10.1016/j.eucr.2019.100919.

    PMID: 31687355
  18. 18

    Solitary Fibrous Tumor of the Right Elbow: A Case Report.

    Mach M, Ostrowski T, Maciejewski K, et al.

    Cureus 2025; (17(7)):e88175 doi:10.7759/cureus.88175.

    PMID: 40687408
  19. 19

    Toward Better Understanding and Management of Solitary Fibrous Tumor.

    Kazazian K, Demicco EG, de Perrot M, et al.

    Surgical oncology clinics of North America 2022; (31(3)):459-483 doi:10.1016/j.soc.2022.03.009.

    PMID: 35715145
  20. 20

    Risk assessment in solitary fibrous tumors: validation and refinement of a risk stratification model.

    Demicco EG, Wagner MJ, Maki RG, et al.

    Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc 2017; (30(10)):1433-1442 doi:10.1038/modpathol.2017.54.

    PMID: 28731041
  21. 21

    Solitary Fibrous Tumors of the Female Genital Tract: A Study of 27 Cases Emphasizing Nonvulvar Locations, Variant Histology, and Prognostic Factors.

    Devins KM, Young RH, Croce S, et al.

    The American journal of surgical pathology 2022; (46(3)):363-375 doi:10.1097/PAS.0000000000001829.

    PMID: 34739418
  22. 22

    Clinical management of extrapleural septal solitary fibrous tumor: A case report.

    Cavaliere M, Piro E, Mascolo M, et al.

    Oncology letters 2020; (20(3)):2465-2468 doi:10.3892/ol.2020.11789.

    PMID: 32782564
  23. 23

    Case Report of Rare Solitary Fibrous Tumour of Nape of Neck with Review of Literature.

    Gupta S, Vaidya AA, Nagireddy TV, Londhe M

    Indian journal of otolaryngology and head and neck surgery : official publication of the Association of Otolaryngologists of India 2024; (76(2)):2026-2031 doi:10.1007/s12070-023-04383-z.

    PMID: 38566660

This overview of Solitary Fibrous Tumor is for educational purposes only. Always consult your oncologist or surgeon for advice on your specific diagnosis and treatment plan.

Stay up to date

Get notified when new research about Solitary Fibrous Tumor (SFT) is published.

No spam. Unsubscribe anytime.