A doctor may use an ultrasound scan as one of the first tests to diagnose and assess a soft tissue sarcoma. An ultrasound can help doctors determine the nature of the lump and plan the most effective treatment.

Soft tissue sarcomas are a rare type of cancer that present as lumps in soft tissues, such as fat, muscle, fibrous tissues, and blood vessels. They account for 1% of all malignant tumors. One of the first assessments for doctors is ultrasound scanning, followed by other imaging and further testing, such as a biopsy.

This article examines how ultrasound detects soft tissue cancer and what a person can expect before and during the scan. It also discusses getting the results and how soft tissue sarcomas present on ultrasound and other tests.

A doctor performing an ultrasound for soft tissue sarcoma.Share on Pinterest
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An ultrasound works by bouncing high-frequency sound waves off areas of the body to create images of organs and other structures. If a doctor suspects soft tissue sarcoma, they may order an ultrasound to:

  • determine whether lumps are solid tumors or fluid-filled cysts
  • determine the location, size, and structure of soft tissue tumors
  • stage cancer by assessing how far it has spread
  • examine how quickly, and in which direction, blood is flowing through vessels
  • guide a needle during a biopsy, aspiration, or other treatment

An ultrasound can detect soft tissue lesions, or tumors, with 80–90% accuracy.

An ultrasound provides images of soft tissue cancers not visible on an X-ray. They are also helpful in distinguishing solid tumors from fluid-filled cysts, as the two make different and distinct echo patterns or sonograms.

Ultrasounds are also convenient because they are quick and do not expose people to radiation.

Learn more about ultrasounds here.

An ultrasound typically occurs in a doctor’s office, hospital, or clinic and is an outpatient procedure, meaning it does not require an overnight stay.

Before the scan, and depending on which organs or body structures the doctors or technicians will be examining, a doctor may advise the patient to:

  • fill their bladder by drinking a large amount of water
  • empty their bowel by taking a laxative
  • have an enema
  • avoid eating or drinking for some time before the scan

For the ultrasound, a person will usually lie on a table and expose the body part for the technician to scan. The technician will spread a special gel over the exposed skin and move a wand-like transducer over the area.

The transducer sends sound waves into the body, and the device records the waves and transforms them into images, called sonograms, on a nearby monitor. The person may also be able to view the images during the ultrasound.

In some people, depending on the area of the body involved, the technician may insert the transducer into the body through the vagina.

After the scan, the technician or the person can wipe the gel off the exposed area. The ultrasound can take between 15 and 45 minutes.

Most people can leave the hospital after the scan and resume normal activities. A person may have to wait a few days for their ultrasound results.

Although ultrasound is a helpful diagnostic tool, doctors cannot always distinguish between malignant and benign tumors from scan results.

If an ultrasound reveals soft tissue tumors, a doctor typically orders further imaging tests and a biopsy.

Learn about the prevalence of soft tissue sarcoma here.

Soft tissue sarcomas vary in appearance on an ultrasound. However, aggressive soft tissue cancers share certain characteristics, including:

  • a shape that is round, oval, or divided into lobes
  • a size greater than 46 millimeters (mm) at the longest diameter
  • a deep location
  • a solid mass with ill-defined margins and many blood vessels

In some people, a soft tissue sarcoma may also have benign characteristics, including:

  • well-defined margins
  • less than 46 mm at the longest diameter
  • minimal or no blood vessels
  • under the skin rather than in a deep location

Because soft tissue sarcomas may have characteristics of benign lesions, doctors need to examine the tumors with other imaging tests and order further tests to reach a diagnosis.

To diagnose soft tissue sarcoma, a doctor will not rely solely on an ultrasound. Other tests may include:

  • Physical examination and health history: A doctor may examine a person by feeling for lumps and swelling, feeling the abdomen, and examining the lungs and body for signs of weakness or abnormalities. They may also question the person about their medical and family health history.
  • Complete blood count (CBC): A doctor may order a CBC test to measure the number and quality of white and red blood cells and platelets.
  • Coagulation test: A coagulation, or blood clotting test, can help doctors check whether the blood is clotting as it should.
  • Further blood tests: Further blood tests, such as blood chemistry tests, can help doctors understand how well specific organs are performing and whether there are abnormalities.
  • X-ray: An X-ray uses small amounts of radiation to produce images of body parts.
  • CT scan: A CT scan uses X-ray equipment to produce detailed cross-sectional 3D images of organs and structures in the body.
  • MRI scan: An MRI scan uses radiofrequency waves and magnets to create highly detailed cross-sectional images of structures in the body.
  • Bone scan: A doctor may use a bone scan to determine whether cancer cells have spread to the bone. The scan uses special radioactive materials that seek out bone tissue to create an image of the bones.
  • Biopsy: In a biopsy, a doctor removes a small amount of tissue from the area of concern for laboratory technicians to examine.

Learn about soft tissue sarcoma treatment here.

An ultrasound is typically one of the first tests a doctor will use to diagnose and assess a soft tissue sarcoma.

Ultrasounds are particularly useful in providing images of soft tissue sarcomas that would not be visible using X-ray. They can help doctors distinguish between fluid-filled cysts and solid masses that are more likely to be tumors. They are also fast and safe, as they do not expose people to radiation.

After an ultrasound, doctors will typically order further tests, such as MRI and CT scans, blood testing, or a biopsy. However, ultrasound images cannot always help doctors distinguish between benign and malignant characteristics in the lesions.