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PubMed This is a summary of 21 peer-reviewed journal articles Updated
Oncology

Is Solitary Fibrous Tumor (SFT) Malignant or Benign?

At a Glance

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.

In this answer

3 sections

01

Moving Beyond “Benign” and “Malignant”

02

The Demicco Risk Model

03

What This Means for Your Care

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].

Common questions in this guide

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 to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Based on my full post-surgical pathology report, what is the Demicco risk score for my tumor?
  2. 2.What was the exact mitotic count, size, and presence of necrosis found in my surgical sample?
  3. 3.Given my specific risk category and the location of my tumor, what does my long-term surveillance and scanning schedule look like?
  4. 4.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

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

Related questions

Is Active Surveillance Safe for Solitary Fibrous Tumors?Will I Need Radiation After SFT Surgery?Are Solitary Fibrous Tumors Hereditary? Causes & RisksCan Solitary Fibrous Tumor (SFT) Come Back Years Later?Where In The Body Do Solitary Fibrous Tumors (SFT) Grow?Do I Need a Biopsy for a Suspected Solitary Fibrous Tumor?What Do Flow Voids Mean on an SFT MRI Report?How Are Brain & Spine Solitary Fibrous Tumors Graded?How to Manage Scanxiety During SFT MonitoringIs Chemotherapy Used for Solitary Fibrous Tumor?What Are Negative Margins in SFT Surgery?What Is SFT Prognosis and Life Expectancy?How Do Solitary Fibrous Tumor Symptoms Vary By Location?What Does STAT6 Positive Mean on a Pathology Report?SFT Follow-Up Schedule: How Often Do I Need Scans?What is Doege-Potter Syndrome in Solitary Fibrous Tumor?Why is Embolization Needed Before SFT Surgery?What Is the Demicco Risk Score for Solitary Fibrous Tumor?What Is the Difference Between SFT and Hemangiopericytoma?What is the NAB2-STAT6 Gene Fusion in SFT?

References

References (21)
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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.

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