Skip to content
Inciteful Med
Resources About us Ask a Question

Is Solitary Fibrous Tumor (SFT) Malignant or Benign?

Published: | Updated:

A solitary fibrous tumor (SFT) is technically a rare soft tissue sarcoma, but it doesn't fit neatly into "benign" or "malignant" categories. Instead, doctors use a personalized scoring system, like the Demicco model, to predict if the tumor is low, intermediate, or high risk for returning.

Key Takeaways

  • • SFTs are classified as tumors with intermediate biological potential, meaning they can act benignly but still have the ability to spread.
  • • Rather than using simple benign or malignant labels, modern medicine uses personalized risk scores to predict an SFT's future behavior.
  • • The Demicco risk model calculates your risk of recurrence based on your age, tumor size, mitotic count, and tumor necrosis.
  • • An accurate risk assessment requires the full pathology report after the tumor has been completely surgically removed.
  • • Your personalized risk score determines your long-term follow-up plan, including how frequently you will need imaging scans.

When patients hear the word “tumor,” the first question is usually: “Is it cancer?” For a solitary fibrous tumor (SFT), the answer does not fit neatly into the standard boxes of “benign” (non-cancerous) or “malignant” (cancerous). The World Health Organization (WHO) classifies SFTs as tumors with intermediate biological potential [1][2]. This means that while most SFTs grow slowly and never spread, they all possess at least some potential to recur locally or spread to other parts of the body (metastasize) over time [3]. Because of this unpredictable behavior and the ability to metastasize, SFTs are technically considered a type of soft tissue sarcoma (a rare cancer), but slapping a simple “malignant” or “cancer” label on them can be misleading, as the majority act in a very non-threatening, indolent way [4][5].

Moving Beyond “Benign” and “Malignant”

Historically, doctors tried to classify SFTs as either strictly benign or malignant based on how the cells looked under a microscope. However, research has shown that this binary classification is flawed. Some tumors labeled “benign” eventually came back, while some labeled “malignant” never caused further issues [6][7].

Roughly 20% of SFTs will behave aggressively [8]. These aggressive tumors typically have specific features visible to a pathologist, such as a high rate of cell division (mitotic rate), areas of dead tissue (necrosis), and tightly packed cells [4]. However, instead of relying on a simple “cancer” label, modern medicine uses personalized risk scores to predict how an individual’s tumor is likely to behave over their lifetime [7].

The Demicco Risk Model

Because the primary treatment for a localized SFT is surgical removal, your medical team will typically use a risk stratification tool on the tumor after it has been completely removed to predict your future risk [9][10]. The most widely used and clinically validated tool for SFTs is the Demicco risk model (often called the D-score), which has been shown to effectively predict clinical behavior across various anatomical sites, from the chest to the abdomen [11][12][13].

Note: While you may have an initial biopsy, an accurate Demicco score usually requires the full post-surgical pathology report, as a small biopsy might miss areas of high cell division or necrosis.

The Demicco model calculates your risk of the tumor returning or spreading by looking at several continuous variables from your post-surgical pathology report:

  • Patient Age: How old you were when diagnosed [14][15].
  • Tumor Size: The maximum measurement of the tumor. Larger tumors carry a higher risk [16].
  • Mitotic Count: How many tumor cells are actively dividing. This is traditionally measured per 10 “high-power fields” (HPF) under a microscope, or in newer reports, per square millimeter (mm²). A count of 4 or more per 10 HPF is generally associated with higher risk [17][18].
  • Tumor Necrosis: Whether there are areas of dead cells within the tumor [12][19].

Based on these factors, the model calculates a score that places your tumor into one of three categories: Low Risk, Intermediate Risk, or High Risk [13][20].

What This Means for Your Care

Understanding your tumor’s risk score is far more useful than knowing if it is called benign or malignant. This personalized score helps your oncology team design the right long-term follow-up plan for you [9]. A low-risk SFT might only require occasional scans (such as once a year) to ensure it hasn’t returned. An intermediate or high-risk SFT might require more frequent, long-term imaging (such as every 3-6 months) and closer surveillance to catch any potential recurrence early [21][10].

Frequently Asked Questions

Is a solitary fibrous tumor considered cancer?
Yes, technically. SFTs are classified as a rare type of soft tissue sarcoma with intermediate biological potential. While most grow slowly and behave non-aggressively, they all possess some potential to recur or spread over time.
What is the Demicco risk model for SFT?
The Demicco risk model is a validated tool doctors use after surgery to predict if your tumor will return or spread. It calculates a risk score based on your age, the tumor's size, its mitotic count, and the presence of dead tissue (necrosis).
Do I need regular scans after my solitary fibrous tumor is removed?
Yes, your follow-up scanning schedule depends on your specific risk score. Low-risk tumors may only need annual scans, while intermediate or high-risk tumors usually require imaging every 3 to 6 months to monitor for recurrence.
Can a biopsy tell me if my SFT is high risk?
A small biopsy might give your team preliminary clues, but an accurate risk score almost always requires the full post-surgical pathology report. A small biopsy sample can easily miss specific areas of high cell division or necrosis within the larger tumor.

Questions for Your Doctor

  • • Based on my full post-surgical pathology report, what is the Demicco risk score for my tumor?
  • • What was the exact mitotic count, size, and presence of necrosis found in my surgical sample?
  • • Given my specific risk category and the location of my tumor, what does my long-term surveillance and scanning schedule look like?
  • • Do we have enough tissue from the initial biopsy to get a preliminary sense of risk, or do we strictly need to wait for full surgical removal to calculate the D-score?

Questions for You

  • • Do I have a complete copy of my post-surgical pathology report that details the size, mitotic rate, and necrosis of my tumor?
  • • How comfortable am I with the "intermediate" nature of this diagnosis, and do I need to seek a second opinion from a sarcoma specialist?
  • • What is my personal tolerance for follow-up testing (like scans), and have I discussed this timeline with my care team?

Want personalized information?

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

References

  1. 1

    Solitary Fibrous Tumor in the Perianal Region: Report of Two Cases With an Atypical Location.

    Gonzalez JA, Sanchez E, Messa Botero O, Cervera-Bonilla S

    Cureus 2021; (13(1)):e12887 doi:10.7759/cureus.12887.

    PMID: 33643733
  2. 2

    Histological and molecular features of solitary fibrous tumor of the extremities: clinical correlation.

    Bianchi G, Sambri A, Pedrini E, et al.

    Virchows Archiv : an international journal of pathology 2020; (476(3)):445-454 doi:10.1007/s00428-019-02650-5.

    PMID: 31463729
  3. 3

    Giant intrapulmonary solitary fibrous tumor.

    Shivalingaiah SDC, Gurumurthy D, Dadich G

    Autopsy & case reports 2024; (14()):e2024494 doi:10.4322/acr.2024.494.

    PMID: 39021462
  4. 4

    CT of retroperitoneal solitary fibrous tumor.

    Ahmed TM, Blanco A, Weisberg EM, Fishman EK

    Radiology case reports 2023; (18(6)):2241-2244 doi:10.1016/j.radcr.2023.03.041.

    PMID: 37123044
  5. 5

    Solitary Fibrous Tumor of the Sigmoid Colon Masquerading as an Adnexal Neoplasm.

    Bratton L, Salloum R, Cao W, Huber AR

    Case reports in pathology 2016; (2016()):4182026 doi:10.1155/2016/4182026.

    PMID: 27672467
  6. 6

    Comparison of published risk models for prediction of outcome in patients with extrameningeal solitary fibrous tumour.

    Demicco EG, Griffin AM, Gladdy RA, et al.

    Histopathology 2019; (75(5)):723-737 doi:10.1111/his.13940.

    PMID: 31206727
  7. 7

    Aggressive Behavior Predictors in Solitary Fibrous Tumor: Demographic, Clinical, and Histopathologic Characteristics of 81 Cases.

    Hassani M, Jung S, Garzia L, et al.

    Annals of surgical oncology 2021; (28(11)):6861-6867 doi:10.1245/s10434-021-09592-w.

    PMID: 33512676
  8. 8

    A Case of Hepatic Malignant Solitary Fibrous Tumor: A Case Report and Review of the Literature.

    Fu Z, Henderson-Jackson EB, Centeno BA, et al.

    Case reports in pathology 2023; (2023()):2271690 doi:10.1155/2023/2271690.

    PMID: 36817074
  9. 9

    Malignant Solitary Fibrous Tumours of the Pleura Are Not All the Same: Analysis of Long-Term Outcomes and Evaluation of Risk Stratification Models in a Large Single-Centre Series.

    Ricciardi S, Giovanniello D, Carbone L, et al.

    Journal of clinical medicine 2023; (12(3)) doi:10.3390/jcm12030966.

    PMID: 36769614
  10. 10

    Management of solitary fibrous tumors localized in extremity: case series and a review of the literature.

    Öztürk R, Arıkan ŞM, Şimşek MA, et al.

    Eklem hastaliklari ve cerrahisi = Joint diseases & related surgery 2017; (28(2)):121-7.

    PMID: 28760129
  11. 11

    Solitary Fibrous Tumour: A Single Institution Retrospective Study and Further Validation of a Prognostic Risk Assessment System.

    Friis RB, Safwat A, Baad-Hansen T, Aggerholm-Pedersen N

    Clinical oncology (Royal College of Radiologists (Great Britain)) 2018; (30(12)):798-804 doi:10.1016/j.clon.2018.08.015.

    PMID: 30206022
  12. 12

    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
  13. 13

    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
  14. 14

    Novel Therapeutic Options for Solitary Fibrous Tumor: Antiangiogenic Therapy and Beyond.

    de Bernardi A, Dufresne A, Mishellany F, et al.

    Cancers 2022; (14(4)) doi:10.3390/cancers14041064.

    PMID: 35205812
  15. 15

    Pathological Features and Clinical Course in Patients With Recurrent or Malignant Orbital Solitary Fibrous Tumor/Hemangiopericytoma.

    Sagiv O, Bell D, Guo Y, et al.

    Ophthalmic plastic and reconstructive surgery 2019; (35(2)):148-154 doi:10.1097/IOP.0000000000001189.

    PMID: 30371551
  16. 16

    Solitary Fibrous Tumor: Integration of Clinical, Morphologic, Immunohistochemical and Molecular Findings in Risk Stratification and Classification May Better Predict Patient outcome.

    Machado I, Nieto Morales MG, Cruz J, et al.

    International journal of molecular sciences 2021; (22(17)) doi:10.3390/ijms22179423.

    PMID: 34502329
  17. 17

    A novel risk score to predict early and late recurrence in solitary fibrous tumour.

    Georgiesh T, Boye K, Bjerkehagen B

    Histopathology 2020; (77(1)):123-132 doi:10.1111/his.14078.

    PMID: 31991494
  18. 18

    CD34-negative Solitary Fibrous Tumor: A Clinicopathologic Study of 25 Cases and Comparison With Their CD34-positive Counterparts.

    Dermawan JK, Rubin BP, Kilpatrick SE, et al.

    The American journal of surgical pathology 2021; (45(12)):1616-1625 doi:10.1097/PAS.0000000000001717.

    PMID: 34152108
  19. 19

    Grading of meningeal solitary fibrous tumors/hemangiopericytomas: analysis of the prognostic value of the Marseille Grading System in a cohort of 132 patients.

    Macagno N, Vogels R, Appay R, et al.

    Brain pathology (Zurich, Switzerland) 2019; (29(1)):18-27 doi:10.1111/bpa.12613.

    PMID: 29600523
  20. 20

    Grade III solitary fibrous tumor/hemangiopericytoma: An enthralling intracranial tumor-A case report and literature review.

    Al Armashi AR, Alkrekshi A, Al Zubaidi A, et al.

    Radiology case reports 2022; (17(10)):3792-3796 doi:10.1016/j.radcr.2022.07.007.

    PMID: 35965927
  21. 21

    Superficial solitary fibrous tumor masquerading as a dermoid cyst: a case report.

    Foss MG, Dunn C, Marks E, Nathoo R

    AME case reports 2022; (6()):34 doi:10.21037/acr-22-17.

    PMID: 36339907

This page explains the biological classification and risk scoring of solitary fibrous tumors for educational purposes. Always consult your oncologist or pathologist to interpret your specific pathology report and risk level.

Stay up to date

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

No spam. Unsubscribe anytime.