To make an accurate diagnosis, your doctor may use one or more tests to check for cancer. Before testing, your physician will consider:
- Your symptoms
- Your overall health
- Your age
- Results from your previous medical tests
- The type of cancer they suspect
Sarcoma Imaging Tests
Usually, the first step in diagnosing sarcoma is an imaging test. Imaging can detect both noncancerous and cancerous tumors. Diagnosing sarcoma can be challenging, so it’s important to see a physician who has experience diagnosing and treating sarcoma.
Imaging tests include:
- Magnetic resonance imaging (MRI): This test uses magnetic fields instead of X-rays to create images of the inside of the body. An MRI can also help your doctor measure the size of the tumor.
- Computed tomography (CT) scan: A CT scan takes X-rays of the body from different angles to create a three-dimensional image that shows tumors or abnormalities.
- Positron emission tomography (PET) scan: During a PET scan, a small amount of a radioactive sugar substance is injected into the body. Cells that use the most energy, such as cancer cells, absorb more of this substance than other cells. Then, a scanner creates images of your organs and tissues.
- Ultrasound exam: An ultrasound creates a picture of the body tissues using sound waves.
If imaging tests show that you have a tumor, your doctor will likely recommend a biopsy. A biopsy is used to confirm a diagnosis. During a biopsy, a physician will remove a small amount of tissue from the affected part of your body.
Your physician may recommend one of the following types of biopsies:
- Needle biopsy: During a needle biopsy, the physician will remove a small tissue sample using a needle-like instrument. They may use MRI, CT or ultrasound imaging to help guide them during the procedure.
- Incisional biopsy: During this procedure, a surgeon will make an incision in your skin and remove part of the tumor for testing.
- Excisional biopsy: During an excisional biopsy, a surgeon will remove the entire tumor. Generally, excisional biopsies aren’t recommended for suspected sarcomas because there is a high risk of the tumor coming back after it’s removed.
Sarcoma Pathology Testing
After a biopsy, the tissue sample is sent to a pathologist (a medical doctor who interprets laboratory tests) for evaluation. The pathologist will look at the tissue sample under a microscope to determine if the tumor’s cells are cancerous or benign. They will also identify the specific proteins, genes and other aspects of the tumor.
The results from the pathology report and additional imaging (such as a CT or PET scan) will help your physician determine what type of sarcoma you have and determine the stage and grade of the tumor.
Cancer staging is used to describe where the cancer began, if it has spread, where it has spread and if it’s affecting other areas of the body. The stage of the sarcoma will inform what type of treatment you may need.
Sarcoma is staged differently depending on where the tumor started. The following staging and grading system is used for soft tissue sarcoma in the trunk, arms, legs and retroperitoneum (area behind the abdominal cavity).
TNM Staging System for Soft Tissue Sarcoma
Doctors use the TNM method to stage many types of cancer, including sarcoma. TNM stands for:
- Tumor (T): This describes the tumor’s size and original location. T is numbered 1 through 4.
- Node (N): “N” describes if the cancer cells have spread to nearby lymph nodes. Lymph nodes are small organs that help the body fight infection. Lymph nodes near the original tumor site are called regional lymph nodes. Lymph nodes in other areas of the body are called distant lymph nodes. Typically, soft tissue sarcoma doesn’t spread to the lymph nodes.
- N0: Cancer cells haven’t spread to the lymph nodes.
- N1: Cancer cells have spread to regional (nearby) lymph nodes.
- Metastasis (M): Metastasis describes if cancer cells have spread to other parts of the body (called distant metastasis).
- M0: Cancer cells haven’t spread elsewhere in the body.
- M1: Cancer cells have spread to other areas of the body.
The answers to these questions will determine the sarcoma’s stage (I through IV, or 1 through 4).
Next, your physician will assess the cancer’s grade (G). The grade describes how much cancer cells resemble healthy cells under a microscope. A tumor’s grade is typically divided into two categories:
- Low-grade or differentiated: This means the cancer cells look similar to healthy tissue under a microscope.
- High-grade or poorly differentiated: This means the cancer cells look very different from healthy tissue under a microscope.
The cancer’s grade can help your physician predict how quickly the cancer will spread.
From there, the tumor’s grade is divided into the following categories:
- GX (grade cannot be determined)
Generally, the lower the grade, the better the prognosis.
Soft Tissue Sarcoma Staging
Your physician will combine the results of your TNM and G classifications to determine the cancer’s stage. Staging will vary based on where the sarcoma began. General groupings include:
- Stage I: The tumor is low grade (GX or G1) and small in size.
- Stage II: The tumor is higher grade (G2 or G3) and small in size.
- Stage III: The tumor is higher grade (G2 or G3) and larger in size.
- Stage IV: The tumor is any size or grade and has spread to other areas of the body.
Once your physician has determined the sarcoma’s stage, they will work with you to develop the appropriate treatment plan.