Sarcoma, Soft Tissue: Diagnosis

Approved by the Cancer.Net Editorial Board, 05/2019

ON THIS PAGE: You will find a list of common tests, procedures, and scans that doctors use to find the cause of a medical problem. Use the menu to see other pages.

Doctors use many tests to find, or diagnose, cancer. They also do tests to learn if cancer has spread to another part of the body from where it started. If this happens, it is called metastasis. For example, imaging tests can show if the cancer has spread. Imaging tests show pictures of the inside of the body. Doctors may also do tests to learn which treatments may work best.

For most types of cancer, a biopsy is the only sure way for the doctor to know if an area of the body has cancer. In a biopsy, the doctor takes a small sample of tissue for testing in a laboratory. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis. Although biopsies have a small chance of not giving a definite answer, they are very important to allow your doctor make a clear diagnosis and develop a clear team-based treatment plan.

This section describes options for diagnosing sarcoma. Not all tests listed below will be used for every person. Your doctor may consider these factors when choosing a diagnostic test:

  • The type of cancer suspected

  • Your signs and symptoms

  • Your age and general health

  • The results of earlier medical tests

There are no standard screening tests for sarcoma. A doctor should examine any unusual or new lumps or bumps that are growing to make sure it is not cancer. Sarcomas are rare. If a sarcoma is suspected, it is very important to talk with a doctor who has experience with this type of cancer.

A diagnosis of sarcoma is made by a combination of clinical examination by a doctor and imaging tests. It is confirmed by the results of a biopsy. In addition to a physical examination, some of the tests described below may be used to diagnose sarcoma.

Imaging tests

Both benign and cancerous tumors can show up on imaging tests, such as an x-ray. Radiologists will use the way the tumor looks on the test to help determine whether it may be benign or cancerous; however, a biopsy is almost always needed.

  • X-ray. An x-ray is a way to create a picture of the structures inside of the body, using a small amount of radiation. X-ray is particularly useful for bone sarcomas, but less valuable for STS.

  • Ultrasound. An ultrasound uses sound waves to create a picture and may be used to look at lumps under the skin or other organs in the body.

  • Computed tomography (CT or CAT) scan. A CT scan takes pictures of the inside of the body using x-rays taken from different angles. A computer combines these pictures into a detailed, 3-dimensional image that shows any abnormalities or tumors. A CT scan can be used to measure the tumor’s size or see if the cancer has spread somewhere else. Sometimes, a special dye called contrast medium is given before the scan to provide better detail on the image. This dye can be injected into a patient’s vein and/or be a pill or liquid the patient must drink.

  • Magnetic resonance imaging (MRI). An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. MRI can be used to measure the tumor’s size. A special dye called a contrast medium is given before the scan to create a clearer picture. This dye can be injected into a patient’s vein. MRI is often used to determine whether a sarcoma can be removed with surgery.

  • Positron emission tomography (PET) or PET-CT scan. A PET scan is usually combined with a CT scan (see above), called a PET-CT scan. However, you may hear your doctor refer to this procedure just as a PET scan. A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of a radioactive sugar substance is injected into the patient’s body. This sugar substance is taken up by cells that use the most energy. Because cancer tends to use energy actively, it absorbs more of the radioactive substance. A scanner then detects this substance to produce images of the inside of the body. This technique can be used to look at both the tumor’s structure and how much energy is used by the tumor and normal tissues. This information can be helpful in planning treatment and evaluating how well treatment is working, but it is usually not performed in all cases of known or suspected STS.

Biopsy and tissue tests

Imaging tests may suggest the diagnosis of sarcoma, but a biopsy will be needed to confirm the diagnosis and to find out the type of sarcoma. It is very important for a patient to see a sarcoma specialist before any surgery or biopsy is done.

  • Biopsy. A biopsy is the removal of a small amount of tissue for examination under a microscope. Other tests can suggest that cancer is present, but only a biopsy can make a reliable diagnosis. A pathologist is a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease.

    Because STS is uncommon, an expert pathologist should review the tissue sample to properly diagnose a sarcoma. Sometimes properly diagnosing a sarcoma requires special tests on the tumor tissue, and it is best if a specialist who sees this type of cancer regularly does this.

    There are different types of biopsies. For a needle biopsy, a doctor removes a small sample of tissue from the tumor with a needle-like instrument—usually a core needle biopsy. This may be performed with the help of ultrasound, CT scan, or MRI to precisely guide the needle into the tumor. In an incisional biopsy, a surgeon cuts into the tumor and removes a sample of tissue. In an excisional biopsy, the surgeon removes the entire tumor. Excisional biopsies are generally not recommended for sarcomas because second surgeries are often needed to completely remove the tumor.

    The type of biopsy and how it is done are important in diagnosing and treating sarcomas, so patients should be seen in a sarcoma specialty center even before the biopsy is performed. Because STS tumors are uncommon and there are many different types of STS, it is important to have an expert pathologist review the sample of tissue removed to appropriately diagnose a sarcoma. People who doctors suspect have sarcoma should be sent to a sarcoma center, ideally before a biopsy is done, so that the treating surgeon can identify the location for the biopsy.

  • Tissue testing of the tumor. Your doctor or the pathologist looking at the sarcoma may recommend running laboratory tests on a tumor sample to identify specific genes, proteins, and other factors unique to the tumor. Results of these tests will help decide what the treatment should be, because each sarcoma can be as different from one another as breast cancer is different from colon cancer (see Types of Treatment).

After diagnostic tests are done, your doctor will review all of the results with you. If the diagnosis is cancer, these results also help the doctor describe the cancer. This is called staging and grading.

The next section in this guide is Stages and Grades. It explains the system doctors use to describe the extent of the disease. Use the menu to choose a different section to read in this guide.