Fibrosarcoma

Fibrosarcoma is a rare type of cancer that begins in the connective tissues of the body, such as tendons and ligaments. Though uncommon, it presents unique challenges depending on whether it affects infants or adults, with the two types behaving very differently.

Table of contents

• What is fibrosarcoma?
• Types of fibrosarcoma
• How common is this condition?
• Body parts affected
• Signs and symptoms
• Causes and risk factors
• How is fibrosarcoma diagnosed?
• Treatment approaches
• Outlook and prognosis

What is fibrosarcoma?

Fibrosarcoma is a rare soft tissue cancer (also called a sarcoma) that develops in the body’s connective tissues, which are the structures that hold parts of your body together^[1]. If you develop fibrosarcoma, you have a cancerous tumor in tissues such as tendons and ligaments. Sometimes, the tumor forms inside bones or in the fibrous tissue covering bone^[1].

This condition is defined as a growth composed of abnormal fibroblasts, which are cells normally found in connective tissue. These cells may produce varying amounts of collagen and have a distinctive pattern when examined under a microscope^[2].

What happens next after diagnosis depends on many factors, including your age, the tumor’s size and location, and whether it has spread to other parts of the body. Your healthcare provider will explain what to expect based on your specific situation^[1].

Types of fibrosarcoma

There are two main types of fibrosarcoma, and they behave very differently from each other^[1].

Infantile (congenital) fibrosarcoma usually appears at birth or shortly after. This type grows fast but rarely spreads to other parts of the body. It is usually curable. Infantile fibrosarcoma is one of the most common soft tissue sarcomas in children under one year of age^[7]. About 90% of infantile fibrosarcomas involve problems with the NTRK gene family. When these genes don’t work properly, tumors can form^[1].

Adult-type fibrosarcoma is most common in adults between 20 and 60 years old, though it can also affect older children and adolescents. Unlike the infantile type, adult-type fibrosarcoma is typically more aggressive and harder to treat^[1]. This type affects middle-aged and older adults most often, and men are affected slightly more than women^[2].

How common is this condition?

Fibrosarcoma is rare in both adults and children^[1]. The adult type accounts for approximately 10% of soft tissue sarcoma diagnoses^[1]. Infantile fibrosarcoma, while one of the most common sarcomas diagnosed in children under five, is still rare overall. It affects fewer than 5 out of 1 million infants^[1].

The number of fibrosarcoma diagnoses has decreased over recent decades as doctors have become better at distinguishing it from other similar tumors^[2].

• Deep soft tissue of the legs (especially shin bone or thigh bone)
• Upper arm
• Knees
• Trunk
• Head or neck (less common)
• Bones

Body parts affected

Fibrosarcoma most often forms in soft tissue deep inside your leg, especially in the shin bone or thigh bone area. It can also develop in the upper arm, knees, or trunk. Less often, tumors start in the head or neck^[1].

In adults, the most common locations are the extremities (arms and legs) at 45%, organs inside the abdomen at 38%, the trunk at 10%, and the head and neck at 5%^[3].

In children, fibrosarcoma most often affects the limbs and trunk of the body, but it can occur in other places^[7].

Signs and symptoms

It usually takes time for fibrosarcoma symptoms to appear. Because fibrosarcoma develops in deep soft tissues, you might not notice any changes in your body until the tumor grows bigger and presses on a nerve or blood vessel^[1].

Common symptoms of fibrosarcoma include^[1]:

• A painless or tender soft lump in your legs, arms, or trunk
• Tingling or “pins and needles” feeling, or sharp, aching, or burning pain (this might be a sign of a pinched nerve near the tumor)
• Unusual swelling (this might be a sign the tumor is pressing on your blood vessels)

In infants, the tumor usually presents as swelling or a lump. Most often there is swelling or a fast-growing mass at birth or shortly after^[7].

If fibrosarcoma starts in your abdomen, you probably won’t notice it until it’s quite large. Then it can start pushing on surrounding organs, muscles, nerves, or blood vessels, leading to pain and tenderness. Depending on the location of the tumor, it can lead to breathing problems^[3].

Fibrosarcoma symptoms can resemble symptoms of other, less serious conditions. Only a healthcare provider can determine whether the changes are because of a fibrosarcoma or a more common, non-cancerous condition^[1].

Causes and risk factors

Researchers haven’t pinpointed exactly what causes fibrosarcoma, but genetic mutations (changes in cells) likely play a role^[1]. Many fibrosarcomas have the same changes in their cell DNA. These changes can cause cells to multiply rapidly and form cancerous tumors^[1].

Researchers have identified some inherited conditions that might increase your risk of developing fibrosarcoma^[1]:

• Familial adenomatous polyposis
• Li-Fraumeni syndrome
• Neurofibromatosis type 1
• Nevoid basal cell carcinoma syndrome
• Retinoblastoma
• Tuberous sclerosis
• Werner syndrome

Other medical conditions associated with fibrosarcoma include^[1]:

• Bone infarction (lack of blood flow causes bone cells to die)
• Chronic (long-term) osteomyelitis
• Fibrous dysplasia
• Paget’s disease of the bone

Risk factors related to your environment and previous medical history include previous radiation therapy directed toward the area where the tumor develops^[1]. Exposure to radiation, chemical exposure, and swelling in the lymph nodes (called lymphoedema) are known risk factors^[4].

Fibrosarcoma can develop as a secondary tumor from a pre-existing problem or after radiotherapy to an area of bone or soft tissue. This type is more aggressive and has a poorer outlook^[3].

How is fibrosarcoma diagnosed?

A specialist doctor will diagnose fibrosarcoma through a series of tests. Careful planning of the initial tests is important to avoid problems with later treatment^[3].

Diagnostic procedures for fibrosarcoma may include^[4]:

• Physical examination — looking at and feeling any lump
• Imaging scans — taking pictures of the inside of the body using scans such as ultrasound, x-ray, CT (computed tomography), MRI (magnetic resonance imaging), or PET (positron emission tomography) scans
• Biopsy — taking and testing a sample of the tumor

Adequate tissue should be obtained through either an image-guided core-needle biopsy or a planned incisional biopsy for select cases. The samples should be reviewed by a pathologist who is experienced in diagnosing sarcomas^[3].

For fibrosarcoma diagnosis in children, a biopsy of the tumor is performed under general anesthesia. The child is not awake and will not feel any pain. The mass or pieces of the mass are removed and looked at under a microscope^[7].

Other tests may be done to see if the disease has spread. These can include CT scan, MRI, bone scans, and bone marrow tests. These tests help to figure out the stage of the cancer and how far it may have spread^[7].

Before any treatment begins, imaging is performed to evaluate the tumor and determine if there are spread to other areas of the body^[3].

Treatment approaches

The main treatment for fibrosarcoma is surgery. The surgeon will remove the tumor and will aim to take out an area of normal tissue as well. This is called “taking a margin” and helps make sure all of the cancer has been removed^[4].

To obtain control of the tumor, surgical removal with a cuff of normal tissue (wide margins) and reconstruction of the resulting defect are necessary. Surgery should only be done when complete patient care is available, including proper biopsy interpretation, access to cancer specialists and radiation specialists, and complete tumor removal^[10].

When fibrosarcoma affects the arms and legs, surgeons will do limb-sparing surgery so that the limb can continue to work well. Although very rare, if the cancer has spread throughout the limb, surgeons may have to perform a partial or full amputation to stop the cancer^[4].

Radiation therapy uses high-energy radiation to destroy cancer cells. It can be used either before or after surgery. When used before surgery, radiation aims to make the tumor smaller so it can be more easily removed. When used after surgery, radiation aims to kill off any remaining cancer cells that were not removed by surgery^[4].

In some cases, the doctor may advise proton therapy instead of radiation therapy. Proton therapy targets the tumor and avoids organs and healthy tissue. This means fewer short-term side effects and long-term problems from radiation^[7].

Chemotherapy uses anti-cancer drugs to destroy cancer cells. It is sometimes used in patients who have a high risk of the cancer coming back or if it has spread to other parts of the body^[4]. The use of chemotherapy is debated among doctors, but it is generally used in bone tumors^[10].

Most often, a combined approach of surgery, chemotherapy, and radiation is used. The treatment plan is based on where the tumor is, if the tumor has spread, the child’s age and health, if the child can tolerate the medicines and procedures, and family preferences^[7].

Researchers have been learning more about treatments called targeted therapies and immunotherapies. Targeted therapy is a treatment that targets specific characteristics within cancer cells to stop them from growing and spreading. Immunotherapy is a treatment that helps the person’s own immune system fight and kill cancer cells. Some of these have worked well in clinical trials of fibrosarcoma, but more research and trials are needed^[4].

Outlook and prognosis

The outlook for fibrosarcoma depends on many connected factors. These include the size and location of the tumor, how abnormal the cells look under the microscope (called the grade), and whether the disease has spread (for example, to the lungs)^[3].

For infantile fibrosarcoma, the outlook is generally good. The disease-free survival rate is about 90%. Studies show no significant survival difference based on margin status, lymph node involvement, or tumor size^[10].

For childhood fibrosarcoma, the prognosis is linked to^[7]:

• The age of the patient (infant versus older children)
• Where the tumor is and if it has spread
• If the tumor was fully removed during surgery

With combined treatment, survival rates are getting better^[7].

In adult fibrosarcoma, about 80% of cases are classified as “high-grade” (Grade 2 or 3). Of the remaining low-grade tumors, 25% progress to high-grade sarcoma over time^[2].

Secondary fibrosarcoma that develops from a pre-existing condition or after radiation therapy is very aggressive and has a much poorer outcome than primary fibrosarcoma^[3].