What Is Fibrosarcoma?

Fibrosarcoma is a rare, highly malignant tumor that results in collagen production in places throughout the body where it should not be. This cancer forms in fibroblast cells responsible for making fibrous connective tissue like tendons that connect muscle to bone. In fibrosarcoma, these cells replicate uncontrollably. 

Fibrosarcomas are usually located deep within tissue or next to bone, although they may be found within bone on rare occasions. When this occurs, tumors usually develop in the long bones—such as the thigh bone, shinbone, and jawbone.

Fibrosarcomas usually impact people during the prime of their lives, with peak incidence rates between 30 and 60 years of age.

This article will provide you with an overview of fibrosarcoma, looking at the types, symptoms, causes, diagnosis, treatment, and overall outlook.

Doctor examining a patient's leg

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Types of Fibrosarcoma

There are two types of fibrosarcoma: infantile or congenital-type fibrosarcoma and adult-type fibrosarcoma. Infantile type fibrosarcoma is less malignant than the adult type and rarely metastasizes.

Childhood Fibrosarcoma

Childhood fibrosarcoma usually affects the long bones of the legs and arms. There are two forms of childhood fibrosarcoma:

  • Infantile or congenital fibrosarcoma occurs in children under 1 year of age and presents as a noticeable mass at or shortly after birth.
  • Adult form fibrosarcoma is similar to the adult form of fibrosarcoma, but it occurs in older children and adolescents, usually between the ages of 10 and 15. It is more aggressive than the infantile form and generally involves more complex treatment.

Adult Fibrosarcoma

Adult type fibrosarcoma can occur anywhere in the body, such as the lungs, and has a higher rate of recurrence after treatment than childhood forms of fibrosarcoma. 

How Fibrosarcoma Presents

Fibrosarcoma symptoms differ based on the age of the patient, and the type, and location of the tumor growth.

Childhood fibrosarcoma symptoms may include:

  • A painless or tender mass in an extremity (an arm or leg) or trunk (stomach or chest)
  • Pain or soreness in muscles near the affected area
  • Limping or other difficulty using legs, feet, arms, or hands, especially in older children

Adult fibrosarcoma symptoms may include:

  • Swelling throughout the body (may be with or without pain), especially the limbs
  • Cough
  • Dark stool
  • Vomiting blood
  • Irregular bleeding from the vagina
  • Pain in the abdomen

What Are the Causes and Risk Factors

The exact cause of fibrosarcoma is unknown but genetic mutations are thought to be behind many cases. Certain gene mutations can lead to fibroblast cells losing control and multiplying excessively.

Soft tissue tumors, such as fibrosarcoma, are more likely to develop in those with certain inherited conditions including:

Other risk factors for fibrosarcoma and other soft tissue sarcomas include chemical exposure to chemicals such as herbicides and arsenic and prior radiation treatment for other cancers.

Pre-existing bone lesions or tissue that has been exposed to radiation during prior cancer treatment may also give rise to secondary fibrosarcomas. This is when a new tumor forms after cancer has spread from the place it first started in the body (such as the bone).

How Fibrosacroma Is Diagnosed

The diagnosis of fibrosarcoma is a difficult one because it's a diagnosis of exclusion. This means that your healthcare provider must rule out all other possible causes of tumor formation before a diagnosis of fibrosarcoma can be made.

A healthcare professional usually takes a detailed medical history and inquires about any soft tissue mass's location, size, shape, and consistency. They may also ask about your cancer history and prior radiation therapy.

Your healthcare provider will perform a focused physical exam, looking specifically at the areas of the body where fibrosarcomas most commonly appear, and check for enlarged lymph nodes.

A healthcare professional may also perform a neurovascular exam. This exam may involve checking your pulse, temperature, and blood pressure, asking about pain, and checking your reflexes and other motor function.

Finally, your oncologist or cancer doctor may order a battery of tests, including:

Taking a biopsy is a useful tool in the diagnosis of fibrosarcoma. Still, the condition shares histological features (tissue structures) with other bone tumors and often cannot be distinguished from other lesions.

Having an experienced musculoskeletal pathologist (a doctor who specializes in diagnosing diseases of the musculoskeletal pathologist) examine the biopsy sample increases the likelihood of making an accurate diagnosis.

Laboratory tests looking at immunohistochemical (IHC) markers (antibodies specific to certain types of cancer) can add more helpful information to make a diagnosis. IHC is especially helpful in identifying specific subtypes of fibrosarcoma. Knowing the tumor's subtype can help inform the best suggestions for treatment.

IHC tumor markers like vimentin, desmin, alpha-smooth muscle actin (α-SMA), muscle-specific actin (MSA), and S-100 have all been associated with fibrosarcoma, but they are not specific to this cancer type; therefore, they cannot be used alone to make a diagnosis of fibrosarcoma.

What Are Treatment Options?

The three main treatment options for fibrosarcoma include surgery, radiation therapy, and chemotherapy.

Surgery is usually the frontline treatment option. The goal of surgery is to completely remove the tumor with an adequate margin or remove a small amount of the surrounding tissue to ensure that all cancer is taken out. This procedure is called a wide excision.

Oftentimes, fibrosarcoma does not respond to radiation therapy or chemotherapy, although it may be used after surgery to reduce the risk of recurrence. 

More recently, research has been exploring new treatment options, such as targeted therapy. This treatment uses drugs or other substances to identify and attack specific cancer cells. For instance, injections of a compound called TIMP-1-GPI fusion protein into fibrosarcoma tumors have been shown to decrease tumor size and growth.

Promising results using stem cells to regulate tumor growth has also provided some hope for more personalized and effective therapeutic approaches in the future.

Prognosis For Fibrosarcoma

Fibrosarcoma tends to be an aggressive and fast-growing cancer, and it has a high rate of recurrence. Soft-tissue fibrosarcoma is associated with a 40% to 60% survival rate at five years, with the most severe forms of fibrosarcoma carrying a much bleaker outlook of 30% survival at five years. The infantile form has a better five-year survival rate, in excess of 80%.

The overall outlook of fibrosarcomas is dependent on several factors such as:

  • Age and overall health
  • Size and location of the tumor
  • Depth and malignancy of the tumor
  • Extent of disease (involvement of nerves, blood vessels, and bone)
  • Density of collagen formed
  • Presence or absence of metastasis
  • Tumor recurrence
  • Response to therapy

Tumors with one or more of the following characteristics carry an especially unfavorable prognosis:

  • Tumor size bigger than 5 centimeters
  • High histologic grade
  • Tumor with a large amount of tissue death (> 50%)
  • Highly mutated cells
  • Collagen fibers with increased cellularity
  • Deeply localized tumors

Summary

Fibrosarcoma is a rare type of soft tissue cancer that affects fibroblast cells. Fibrosarcoma causes these cells to overproduce collagen, which results in a tumor. Treatment usually involves surgery. This cancer is aggressive and fast-growing, so it's important that it be caught early and treated as soon as possible for the best possible prognosis.

A Word From Verywell

If you or a loved one are experiencing symptoms of fibrosarcoma, such as a lump that is increasing in size, becoming more painful over time, or a lump felt on deep-pressure touch, seek immediate medical attention.

Fibrosarcoma is very rare, so it's unlikely that your symptoms will lead to this diagnosis, but identifying the cause of the mass and any other symptoms can bring you peace of mind and help ensure you get an early diagnosis and treatment if cancer is suspected. This is critical to improving your overall outlook and giving you the best chance of living a cancer-free life moving forward.

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6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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