How Are Brain & Spine Solitary Fibrous Tumors Graded?

Solitary fibrous tumors (SFTs) located in the central nervous system (CNS)—the brain and spinal cord—are graded differently than SFTs found elsewhere in the body. If your SFT is in your brain or spine, your pathology report will use the 2021 WHO Classification of Tumours, which assigns a Grade 1, 2, or 3 ^[1][2]. In contrast, SFTs in the soft tissue (like the limbs, abdomen, or chest) are typically assessed using the Demicco risk score ^[3]. Because the brain and spine are closed, highly sensitive environments, standard soft tissue scoring systems do not accurately predict how a tumor will behave in the CNS ^[4].

The WHO Grading System for Brain and Spine SFTs

In the past, higher-grade SFTs in the brain were commonly called “hemangiopericytomas.” You might still see this term in older research, and some doctors may still use it out of habit, but the 2021 World Health Organization (WHO) update officially combined them under the single name “solitary fibrous tumor” ^[5]. Pathologists now determine the tumor’s grade by looking at a biopsy sample under a microscope and evaluating specific features ^[1]:

• Grade 1: These tumors are considered lower risk. They are hypocellular (having fewer cells spread further apart) and contain a lot of collagen (connective tissue) ^[1][6]. They have a low mitotic rate—meaning very few cells are actively dividing (typically fewer than 5 dividing cells per 10 high-power fields, or per mm², under the microscope) ^[1].
• Grade 2: These tumors look structurally different from Grade 1. They are highly cellular, meaning the cells are packed densely together ^[1]. However, like Grade 1, they still have a relatively low mitotic rate (fewer than 5 dividing cells per 10 high-power fields) and no tissue death ^[1].
• Grade 3 (sometimes historically called Anaplastic): These are the most aggressive CNS SFTs. To be classified as Grade 3, a tumor typically shows a high mitotic rate (5 or more dividing cells per 10 high-power fields or per mm²) ^[1][7]. Pathologists also look for necrosis, which are areas of dead tumor tissue caused by the tumor growing faster than its blood supply ^[1]. Grade 3 tumors have a higher risk of growing back locally or spreading outside the nervous system ^[8].

Why the Demicco Score Isn’t Used for the Brain

If you have been reading general information about SFTs online, you have likely seen references to the Demicco risk score. This tool is widely used for soft tissue SFTs in the body to predict the likelihood of the tumor spreading (metastasizing) ^[9].

The Demicco score relies heavily on three factors: the patient’s age, the tumor’s mitotic count, and the size of the tumor ^[10]. Specifically, it assigns higher risk points for tumors that are 10 centimeters (about 4 inches) or larger ^[10].

However, this system does not work well for brain or spine tumors for a few key reasons:

• Size means something different in the brain: A 10-centimeter tumor in the thigh might be caught relatively early and be fairly easy to remove. A 10-centimeter tumor in the skull is massive, immediately life-threatening, and severely constrained by the tight space of the skull ^[4].
• Different clinical risks: Soft tissue SFTs are primarily evaluated for their risk of spreading to other organs ^[9]. While brain SFTs can spread, the most immediate and common risk is local recurrence—the tumor growing back in the same spot where it was removed ^[11].
• Surgical factors matter more: In the CNS, whether the surgeon could remove the entire tumor (gross total resection) is often the most important predictor of a patient’s outcome ^[8][12]. Soft tissue models like Demicco simply don’t account for how difficult it is to safely remove a tumor from sensitive brain or spinal tissue ^[4].

What Your Grade Means for Treatment

Your WHO grade helps your neurosurgeon and neuro-oncologist decide on the best follow-up plan after your surgery.

• Complete Removal is Key: For all grades, safely removing as much of the tumor as possible is the primary goal ^[8].
• Radiation Therapy: If you have a Grade 3 SFT, or if your surgeon was only able to perform a partial removal (subtotal resection) of a Grade 1 or 2 tumor, your care team will likely recommend radiation therapy to help prevent the tumor from returning ^[13][14].
• Long-Term Monitoring: Because CNS SFTs can sometimes recur many years after treatment regardless of their initial grade, you will need monitoring for a very long time—often for life ^[15]. This includes regular MRI scans of your brain and spine. Because higher-grade tumors carry a risk of spreading outside the nervous system, your team may also recommend systemic monitoring, such as CT scans or PET scans of your chest and abdomen ^[8][15].