Is a Solitary Fibrous Tumor a Sarcoma?

A soft fibrous tumor (SFT) is considered a translocation-related soft tissue sarcoma that can be divided into three types based on the presence or absence of histological characteristics linked to a more aggressive clinical presentation. 

SFTs can develop anywhere in the soft tissues (pleura). SFTs are primarily discovered in the lining of the lungs, but they have also been identified in the head and neck, breast, kidney, prostate, spinal cord, and other locations. Most solitary fibrous tumors are benign but can be malignant in rare cases.

Like other soft tissue sarcoma subtypes, SFTs primarily affects adults in their 50s and 60s. SFTs can be benign or malignant, and evidence suggests that the risk of metastasis is correlated with age at diagnosis and tumor size.

The metastatic potential of a solitary fibrous tumor (SFT) is low. The high-grade or dedifferentiated variant has a higher metastatic rate. 

Although metastasis occurs in 5%-25% of people with SFT, it is challenging to determine whether tumors and other medical factors in the person predict the aggressiveness of the disease. The lungs and liver are the most expected sites of distant spread. Bone involvement is generally considered a late stage of disease progression.

People with sarcoma, particularly those with metastatic cancer, require multidisciplinary treatment. Local therapies can be evaluated within the framework of an interdisciplinary team with limited retrospective and prospective evidence to guide therapy.

Solitary fibrous tumors (SFTs) grow slowly and may not cause symptoms until they are very large. Small tumors seldom cause any symptoms. However, if they pressure the surrounding structure, they may become uncomfortable.

Common signs and symptoms of SFTs include:

• Palpable mass
• Slow tumor growth
• Chest pain
• Persistent cough
• Shortness of breath
• Limited joint movement
• Swelling (clubbing) of fingers or toes
• Increased temperature over the tumor
• Abnormal dilation of superficial blood vessels, appearing as red, blue, or purple over the tumor
• Dilated veins in the area of the tumor
• Abnormal pulsations or sounds heard on auscultation over the tumor
• Proptosis (eye bulging) or but ptosis (eyelid drooping)
• Eyelid swelling
• Visual disturbances
• Sometimes, hypoglycemia (sweating, dizziness, confusion, alteration in mental status, cold hands)

Currently, researchers are unsure what factors could trigger a solitary fibrous tumor (SFT). There are currently no well-defined risk factors for SFTs. Potential causes and risk factors include the following:

• Genetics: SFTs frequently have mutations in NGFI-A-binding protein 2 (NAB2), STAT6, TP53, BCOR, and SETD2 genes. The recurrent body aggregation of two genes, NAB2 and STAT6, located on chromosome 12q13, has been identified in monofilament SFTs.
• Doege-Potter syndrome: Paraneoplastic Doege-Potter syndrome, brought on by IGF-2 production in the tumor, is linked to some SFTs.
• Age: The tumor can appear in people between ages 20-70, but it is usually discovered between ages 40-50. It is less commonly found in children and infants.
• Sex: In general, SFTs occur more often in men than in women. SFTs in the abdominal wall, however, are more common in women.
• Previous cancer treatments: Having previously received radiation therapy for cancer treatment is one factor that can increase the risk of developing SFTs.

SFTs are rare tumors with a 2.8/100,000 overall incidence. There is no known link between environmental exposure to radiation, tobacco, asbestos, other toxins, or any inherited risk factors. They may be linked to genetic mutations, but more research is needed to understand these anomalies.

There is no standard treatment regimen for solitary fibrous tumors (SFTs). The primary objective of treatment for SFTs is to remove the tumor and prevent a recurrence. 

Surgery

• Depending on tumor size and location, surgery could be considered an option.
• Surgery for SFTs involves removing the tumor and a small amount of the surrounding healthy tissue. This can provide the person with a cure, especially if the tumor is benign.
• People may require long-term follow-up after the surgical procedure to monitor their progress. Even benign tumors can develop metastasis after several years.
• Recurrence of the cancer is most common within the first 24 months following surgery, both locally and distantly at the former location of the tumor. Given the lack of well-documented evidence for modern cancer therapies, surgical resection remains the therapy of choice in the case of recurrence.

Radiation therapy

• High-powered energy beams (X-rays) are used to shrink the tumor so that it can be removed entirely during surgery.
• Radiation may be the main therapy when the tumor cannot be entirely excised or when dealing with a recurrent SFT following surgery.
• It can also be used as adjunctive therapy after surgery if there is a risk of tumor recurrence or there are insufficient margins.

Chemotherapy

• Chemotherapy is used when the tumors cannot be removed completely due to:
  • Incomplete surgical resection
  • Recurrence after surgery
  • Tumors have spread to distant parts of the body (metastatic SFTs)

Targeted therapy or antiangiogenics

• With targeted therapy, certain medications are used to interfere with the signaling pathways of vascular endothelial growth factor and other tyrosine kinases. These routes affect the blood supply to the tumor and can inhibit the growth of advanced SFTs.
• Though immunotherapy's therapeutic potential remains uncertain, the use of antiangiogenics as first-line therapy is being positively studied.

Arterial embolization

• Some people with SFT may benefit from this procedure, which involves cutting the blood supply to the tumor, eventually killing it.

Corticosteroids

• Corticosteroids may be used to treat hypoglycemia brought on by the tumor.

Prevention and recovery

• Maintain minimum activity levels
• Practice a healthy lifestyle
• Regular medical screening at periodic intervals with blood tests, radiological scans, and physical examinations

For solitary fibrous tumors (SFTs) that have been completely excised, the prognosis is excellent. Studies have shown that approximately 75% of have a benign course, with the remaining 25% exhibiting invasion to adjacent tissues, recurrence, or distant metastasis.

About 95% of recurrent tumors have benign histopathology, and up to 75% of histopathology-confirmed malignant tumors have nonaggressive clinical behavior.

Tumor recurrence has been documented to occur as soon as 3 months and as late as 40 years after primary removal. Approximately 63% of people with SFTs will experience tumor recurrence, with more than half succumbing to disease progression within 2 years.

Timely diagnosis and treatment are linked to better outcomes. Because of the increased likelihood of local recurrence, close interval follow-up is advised.