How Fibrosarcoma Is Diagnosed

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Fibrosarcoma is a rare soft tissue tumor that is aggressive and fast growing. This type of cancer causes excessive collagen production in places throughout the body where it should not be. There are two types of fibrosarcoma: adult fibrosarcoma and infantile, or childhood, fibrosarcoma.

The diagnosis of fibrosarcoma is a difficult one because symptoms are often nonspecific, mimicking many other conditions. Fibrosarcoma is a diagnosis of exclusion, which means that all other possible causes of tumor formation must be ruled out before a diagnosis of fibrosarcoma can be made.

This article will review the tests and procedures used to diagnose fibrosarcoma.

Woman prepping for an MRi

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What Happens During a Physical Examination?

Proper diagnosis of fibrosarcoma requires some level of clinical suspicion of cancer and a focused physical exam. Your healthcare provider will take your vitals (temperature, blood pressure, and heart rate) and check your weight since fibrosarcoma can present with sudden weight loss.

Your healthcare provider may want to examine specific areas of the body where fibrosarcomas most commonly appear, looking for raised areas and palpating (feeling by touch) your arms, legs, head, and neck.

Additionally, your doctor or another healthcare professional may perform a neurovascular exam. This is an assessment of your pulse, temperature, levels of pain, physical sensation, and motor function in the affected limb.

Your healthcare provider may also check for enlarged lymph nodes and ask you to walk in a straight line. This walking test observes your balance and coordination, as advanced fibrosarcoma can disrupt blood circulation and limit your movement.

What Labs and Tests Are Used?

If cancer is suspected, it is likely that your healthcare will order a battery of lab tests.

Your healthcare provider will likely order a biopsy. This is a procedure in which a sample of the tumor is removed using a surgical tool or needle. A biopsy is usually performed during surgery or with local anesthesia. For fibrosarcoma, a core needle (a larger hollow needle) is often used to remove multiple small pieces of the tumor to be examined.

Tissue samples from a biopsy are then sent to a lab to be examined under a microscope and tested. A biopsy can lead to a definitive diagnosis, but it's important to keep in mind that fibrosarcoma shares histological (structural) features with many bone tumors and often cannot be distinguished from other lesions. Tissue examination by an experienced musculoskeletal pathologist increases the likelihood of making an accurate diagnosis.

In later stages, fibrosarcoma can cause nutritional deficiencies, anorexia (loss of appetite), and weight loss, so blood tests may be ordered to establish your baseline of health and help gather information for a diagnosis. Tests ordered may include:

  • A complete blood count (CBC)
  • Urea and electrolyte levels, such as sodium, potassium, chloride, and bicarbonate, to make sure the kidneys and other organs are working properly
  • Liver function tests 

You can eat and drink normally before most blood tests, but your healthcare provider may ask you to fast for a few hours beforehand.

In addition to blood tests, your healthcare provider may also ask for cytogenetic tests. These lab tests analyze blood or other tissue samples to look for mutations in chromosomes or genes.

These genetic tests can indicate if you have an increased risk for certain types of cancer. Genetic tests can help rule out other causes and may later inform the best treatment options and practices if you are diagnosed with cancer. These include tests that look for:

  • TP53 tumor suppressor gene that is also linked to the development of other types of sarcomas (types of bone or tissue cancer) such as rhabdomyosarcoma, leiomyosarcoma, and liposarcoma
  • Mutations in the neurofibromatosis 1 (NF1) gene, which causes tumors to develop around nerves
  • Mutations in the retinoblastoma (RB1) gene, a cause of a rare eye cancer in children
  • Mutation in the TSC1 or TSC2 gene, which causes tuberous sclerosis, a rare genetic condition in which benign tumors grow in various organ systems

Imaging Tests for Fibrosarcoma

Imaging is more helpful for detecting other conditions without actually identifying fibrosarcoma. But remember that fibrosarcoma is a diagnosis of exclusion, so this is an important step in the diagnostic process. Your healthcare provider may order a number of imaging tests, including:

  • X-rays: Plain radiographs are usually the first imaging type used by healthcare professionals because X-rays are cheaper and quicker to take than other imaging tests.
  • Computed tomography (CT) scans: CT scans may be helpful when fibrosarcomas affect bone by quantifying the destruction caused by the tumor and the amount of intact bone that is left.
  • Magnetic resonance imaging (MRI) scans: MRIs are great for examining soft tissue abnormalities in the affected limb.
  • Positron-emission tomography (PET) scans: PET scans can measure the biological activity of the tumor. PET Scans are still being studied to determine the efficacy of this tool for staging and monitoring treatment response.
  • Ultrasound scans: Ultrasounds are usually performed prior to taking a biopsy.

Differential Diagnoses

It’s important to remember that fibrosarcoma is incredibly rare so if you’re feeling some pain or detect a lump, it’s probably something more benign (harmless).

If you are generally healthy with little or no cancer risk factors, the chances of you having fibrosarcoma are even lower. Still, the following conditions must be ruled out before making a diagnosis of adult fibrosarcoma:

  • Nodular fasciitis (a benign lump that grows in soft tissue)
  • Myositis ossificans (rare bone formation within a muscle)
  • Osteosarcoma (bone cancer)
  • Leiomyosarcoma (cancer of smooth muscle tissue)
  • Desmoid tumor (benign soft tissue tumor)
  • Malignant peripheral nerve sheath tumor (MPNST, cancer of cells that protect the nerves)
  • Fibroma of tendon sheath (a rare benign tumor that often forms in the hand)

The following are additional conditions that must be considered when making a diagnosis of childhood fibrosarcoma:

  • Myofibroma (benign fibrous tumor)
  • Infantile fibromatosis (rare benign tumor)
  • Monophasic synovial sarcoma (a soft tissue cancer)
  • Embryonal rhabdomyosarcoma, particularly spindle cell variant (rare skeletal muscle cancer)
  • Dermatofibrosarcoma protuberans (very rare type of skin cancer)
  • Primitive peripheral neuroectodermal tumor (soft tissue tumor)

Summary

Fibrosarcoma is a tricky cancer to diagnose. As such, it is a diagnosis of exclusion, meaning that your healthcare provider will have to rule out all other causes of your symptoms to reach a diagnosis of fibrosarcoma. Diagnostic tests for fibrosarcoma include a physical exam, bloodwork, biopsy, and imaging tests, including X-rays, MRIs, and PET scans.

A Word From Verywell

Fibrosarcoma is very rare. Still, it should be considered if you have had prior exposure to radiation therapy, massive scar tissue formation after a burn or injury, or high hereditary or genetic cancer risk—and are therefore at higher risk of developing this disease.

Getting an accurate diagnosis usually takes a high level of suspicion and a healthcare provider who knows what to look for, such as swelling, pain, or a noticeable lump in a limb. Seek out a knowledgeable and experienced healthcare provider who can be helpful in making a quick diagnosis that increases your likelihood of getting timely treatment.

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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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