Causes and Diagnoses

Causes and Diagnoses of Sarcoma

The DNA of the cells in your soft tissue or bones can change turning healthy cells into cancer cells. This is what causes sarcomas. When the cancer cells grow without stopping, they may form a tumor.

Scientists do not know what makes healthy cells become a sarcoma for most patients.

Risk factors are things about you — such as your health history, family history or exposure to chemicals — that can put you at a higher risk for a disease or condition. For most sarcomas, there are no known risk factors.


Your care team needs a tumor sample from a biopsy or a surgery to determine if you have a sarcoma.

Getting an accurate diagnosis is important because it helps your care team make an effective treatment plan. Because sarcomas are so rare, many physicians are not familiar with them. To get an accurate diagnosis, find a specially trained expert with experience in treating sarcoma.


Your care team will likely do a biopsy. A surgeon or radiologist will remove a sample of tissue from your tumor. Then, a pathologist will study it under a microscope and perform more lab tests to see if the tumor is cancer.

Pathologists are physicians who diagnose medical conditions. They use lab tests and study samples of your body fluids (such as urine or blood) or tissue (such as bone or muscle). Choose a hospital with a pathologist who has experience with sarcomas to help ensure you get an accurate diagnosis.

There are several types of biopsies commonly used to diagnose sarcoma:

  • Excisional biopsy: If your tumor is small, a surgeon can take out the whole tumor. You will get anesthesia so you are asleep during the biopsy.
  • Incisional biopsy: If your tumor is big, the surgeon removes only a small part of it. If the tumor is close to your skin's surface, they may numb the area. If the tumor is deep in your body, you will be asleep during the procedure.
  • Needle biopsy: Your physician puts a thin needle through your skin to remove tiny bits of tissue from the tumor. This type of biopsy does not require surgery. You are awake during this test. The physician may use a CT scan to guide the needle. This is the most common way that sarcoma is diagnosed.

After a biopsy, you and your care team will get a pathology report that may include:

  • A diagnosis
  • A description of the tumor
  • Staging information
  • More lab tests (such as immunohistochemical stains and molecular tests)

Imaging Studies

Imaging studies are very important for diagnosing sarcoma. They help your care team learn how advanced the cancer is and develop a treatment plan. Your care team may use one or more of these tests, including:

  • X-ray: Uses small amounts of radiation to take pictures of your bones and soft tissue.
  • Computed tomography scan (CT scan): A CT scanner takes X-rays of your body from different angles as you slide through it on a table. A computer combines these pictures to make a detailed picture of the inside of your body.
  • Magnetic resonance imaging (MRI): Large magnets and radio waves make detailed pictures. These will help your physician take a sample for a biopsy.
  • Bone scan: For this test, a nurse or technician injects you with radioactive dye. About 2 hours later, they will take pictures of your bones with a special camera. The dye will show where there is a lot of radiation. That can mean there are abnormal cells in that area.
  • Positron emission tomography (PET) scan: For this scan, a slightly radioactive sugar is injected into your blood. Tumors use more of this sugar than normal cells, so the radiation collects in tumors. This helps your care team see it with a special camera. PET scans help your care team see if a tumor is spreading to other parts of your body. They can also help your care team watch how a tumor responds to treatment.