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Understanding Your Risk: Grading and Staging

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Doctors assess Solitary Fibrous Tumor (SFT) risk using specific grading systems rather than standard cancer staging. For tumors in the body, the Demicco Risk Score uses age, size, and cell growth to predict outcomes. For brain and spine tumors, the WHO Grading system (1-3) is used. These scores guide treatment and monitoring plans.

Key Takeaways

  • • Solitary Fibrous Tumors do not use standard cancer staging; they use risk models based on tumor location.
  • • The Demicco Risk Score evaluates soft tissue SFTs based on age, tumor size, mitotic count, and necrosis.
  • • Brain and spine SFTs are classified by the WHO grading system as Grade 1, 2, or 3.
  • • High mitotic count (rapid cell division) and necrosis are key indicators of a higher-risk or malignant tumor.
  • • Higher risk scores often lead to recommendations for adjuvant radiation and more frequent surveillance scans.

Because Solitary Fibrous Tumors (SFT) are unpredictable, doctors don’t use the standard “Stage 1 through 4” system used for many other cancers. Instead, they use specialized risk models and grading systems to estimate how likely a tumor is to return or spread [1][2].

For Tumors Outside the Brain and Spine: The Demicco Risk Score

For SFTs in the chest (pleura) or soft tissues, the Demicco Risk Score is the most widely used tool [3][4]. It combines four specific pieces of information to categorize your risk as Low, Intermediate, or High [1][5]:

  1. Age: Older age (typically over 55) can contribute to a higher score [5].
  2. Tumor Size: Larger tumors (especially those over 10 or 15 cm) are generally considered higher risk [5].
  3. Mitotic Count: This is a measure of how fast the cells are dividing. A count of 4 or more per 10 high-power fields (a specific microscope view) often signals a more aggressive tumor [6][7].
  4. Necrosis: This refers to areas of dead tumor cells. Its presence usually indicates the tumor is growing faster than its blood supply can support, which is a sign of higher risk [5][8].

What the Score Means for You:

  • Low Risk: These tumors are very unlikely to spread (metastatize) and are often cured by surgery alone [5].
  • Intermediate/High Risk: These tumors have a higher chance of returning or spreading, meaning you will likely need more frequent scans and possibly additional treatments like radiation [9][10].

For Brain and Spine Tumors: WHO Grading

For SFTs in the Central Nervous System (CNS), the World Health Organization (WHO) uses a three-tiered grading system rather than the Demicco score [11][12].

  • Grade 1: Historically called “typical” SFT. These are slow-growing and have the best outlook [13][14].
  • Grade 2: These tumors have more active cell division (higher mitotic count) and a higher risk of coming back [13].
  • Grade 3: Previously called “anaplastic” SFT or malignant Hemangiopericytoma. These are the most aggressive, showing very high cell division and often areas of necrosis [13][15]. They have a significantly higher risk of spreading outside the CNS [16].

Defining ‘Malignant’ SFT

While most SFTs are “intermediate,” doctors may use the term malignant if the tumor meets specific criteria [17]. Generally, this means the tumor has a high mitotic count (at least 4 per 10 HPF) along with other “worrying” features like necrosis, high cellularity (densely packed cells), or significant cell abnormalities (atypia) [18][19].

How Scores Guide Your Treatment

Your risk score or grade is the “roadmap” for your care team [20]:

  • Surgery: Regardless of the grade, the goal is always Gross Total Resection (GTR)—removing the entire tumor [21][22].
  • Adjuvant Radiation: If you have a high-risk or Grade 2/3 tumor, or if the surgeon couldn’t remove the whole mass, your doctor may recommend radiation to kill any remaining cells [23][24].
  • Surveillance: Patients with higher risk scores will need more frequent imaging (like MRI or CT scans) and longer-term follow-up—sometimes for life—because SFTs can return even a decade after surgery [25][26].

Frequently Asked Questions

Is Solitary Fibrous Tumor staged like other cancers?
SFTs typically do not use the standard Stage 1 through 4 system used for other cancers. Instead, doctors use specialized risk models like the Demicco Risk Score (for body tumors) or WHO Grading (for brain/spine tumors) to estimate the likelihood of the tumor returning or spreading.
What is the Demicco Risk Score?
The Demicco Risk Score is a tool used to categorize risk for SFTs located in the soft tissues or pleura (chest). It calculates a score based on the patient's age, tumor size, mitotic count (cell division rate), and the presence of necrosis (dead tissue).
What is the difference between WHO Grade 1, 2, and 3 SFT?
For SFTs in the brain or spine, doctors use the World Health Organization (WHO) grading system. Grade 1 tumors are slow-growing with the best outlook, while Grade 3 tumors (formerly called anaplastic) are aggressive, have high cell division rates, and are more likely to spread.
What does a high mitotic count mean in an SFT pathology report?
Mitotic count measures how fast tumor cells are dividing under a microscope. A count of 4 or more per 10 high-power fields suggests the tumor is growing more aggressively, which contributes to a higher risk score or grade.
When is an SFT considered malignant?
While most SFTs are intermediate, doctors may classify a tumor as malignant if it shows aggressive features. These include a high mitotic count, presence of necrosis (dead cells), high cellular density, or abnormal cell shapes.
How does the risk grade affect my treatment plan?
Your risk score helps doctors decide if surgery alone is enough or if additional treatments like radiation are needed. Higher-risk tumors also require more frequent imaging scans and lifelong surveillance because they have a higher chance of coming back.

Questions for Your Doctor

  • • What is my Demicco risk score based on my age, tumor size, and pathology?
  • • For my CNS tumor, what specific criteria (mitotic count, necrosis) were used to assign it a WHO Grade 1, 2, or 3?
  • • Does my tumor show any 'high-risk' features like necrosis or a high mitotic count (4 or more per 10 high-power fields)?
  • • How does my risk score or grade specifically change my long-term imaging and surveillance plan?
  • • Given my grade/risk score, do you recommend adjuvant radiation to reduce the chance of the tumor coming back?

Questions for You

  • • How old were you at the time of your diagnosis? (This is one factor in some risk models.)
  • • Was your tumor completely removed during surgery, or was some left behind?
  • • Has your doctor used the terms 'low risk' or 'high risk' when talking about your prognosis?
  • • Where exactly in your body was the tumor located—in the brain/spine or elsewhere?

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This guide explains SFT risk assessment and grading systems for educational purposes. Only your medical team can determine your specific prognosis and treatment plan based on your full pathology report.

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