The stage of a cancer is how much and how far the cancer has spread in your body. Your doctor uses exams and tests to find out the size of the cancer and where it is. They can also see if the cancer has spread to nearby areas, and if it has spread to other parts of your body. The stage of a cancer is one of the most important things to know when deciding how to treat the cancer.

Soft tissue sarcomas are usually staged with the TNM staging system from the American Joint Committee of Cancer. The staging system is complex, so ask your doctor to explain all the letters and numbers.

The first step in staging is to find the value for each part of the TNM system. Here's what the letters stand for:

• T describes the size of the main tumor.
• N describes whether or not the cancer has spread to nearby lymph nodes.
• M denotes if the cancer has spread (metastasized) to distant parts of the body.

Numbers or letters after T, N, and M provide more details about each of these factors. There are also two other values that can be assigned:

• X means the provider does not have enough information about the main (primary) tumor (TX) or the lymph nodes in the region near the primary tumor (NX).
• 0 means no sign of cancer, such as no sign of lymph node spread (N0).

Grade is another key part of staging these cancers. The grade is based on the French FNCLCC system using three factors: differentiation, mitotic count, and tumor necrosis.

G is the grade of the cancer. This is a measure on a scale of one to three (G1, G2, and G3) of how quickly the cancer is likely to grow and spread. It's based on how the cancer cells look under the microscope. Each factor is given a score, and the sum of the three factors determine the grade of the tumor. G1 has a total score of 2 or 3. G2 has a score of 4 or 5. And G3 has a total score of 6, 7, or 8. Higher-grade cancers are more likely to grow and spread quickly.

The letter X may be used when the grade isn't known (GX).

These four factors, T, N, M, and G, are combined to give an overall description of your cancer and the sarcoma an overall stage grouping.

A stage grouping is listed as a Roman numeral and can have a value of I through IV (1 to 4). The higher the number, the more advanced the cancer is. Letters and numbers can be used after the Roman numeral to give more details.

Soft tissue sarcomas start in cells that make up parts of the body like muscle, nerves, fat, vessels, and fibrous tissue. As the cancer grows, it can spread into nearby tissues and vessels. Then, like all cancers, it can spread (metastasize) to other parts of the body. That's why you might hear cancer that has spread being called metastatic cancer.

The stages of soft tissue sarcoma depend on where the cancer is. There are two main groups: sarcomas that start in the trunk and limbs and sarcomas that start in the back of the belly (abdomen) in an area called the retroperitoneum. Both are covered here.

These are the stage groupings for soft tissue sarcomas that start in the trunk and limbs (arms and legs) and what they mean:

Stage IA. The main tumor is 5 centimeters (cm) across or less. It has not spread to nearby lymph nodes or to other parts of the body. It's either low grade (G1) or the grade isn't known (GX).

Stage IB. The main tumor is more than 5 cm across. It has not spread to nearby lymph nodes or to other parts of the body. It's either G1 or the grade isn't known (GX).

Stage II. The main tumor is 5 cm across or less. It has not spread to nearby lymph nodes or to other parts of the body. It's either G2 or G3.

Stage IIIA. The main tumor is 5 cm to 10 cm across. It has not spread to nearby lymph nodes or to other parts of the body. It's either G2 or G3.

Stage IIIB. The main tumor is more than 10 cm across. It has not spread to nearby lymph nodes or to other parts of the body. It's either G2 or G3.

Stage IV. The tumor is any size and has spread to nearby lymph nodes. It has not spread to other parts of the body. It can be any grade. Or the tumor is any size and has spread to nearby lymph nodes. It has also spread to other parts of the body, like the lungs. It can be any grade.

These are the stage groupings for soft tissue sarcomas that start in the back of the belly (the retroperitoneum) and what they mean:

Stage IA. The main tumor is 5 centimeters (cm) across or less. It has not spread to nearby lymph nodes or to other parts of the body. It's either low grade (G1) or the grade isn't known (GX).

Stage IB. The main tumor is more than 5 cm across. It has not spread to nearby lymph nodes or to other parts of the body. It's either G1 or GX.

Stage II. The main tumor is 5 cm across or less. It has not spread to nearby lymph nodes or to other parts of the body. It's either G2 or G3.

Stage IIIA. The main tumor is 5 cm to 10 cm across. It has not spread to nearby lymph nodes or to other parts of the body. It's either G2 or G3.

Stage IIIB. This stage is either of these:

• The main tumor is more than 10 cm across. It has not spread to nearby lymph nodes or to other parts of the body. It's either G2 or G3.
• The tumor is any size and has spread to nearby lymph nodes. It has not spread to other parts of the body. It can be any grade.

Stage IV. The tumor is any size and has spread to nearby lymph nodes. It has also spread to other parts of the body, like the lungs. It can be any grade.

After your cancer is staged, talk with your doctor about what the stage means for you. Make sure to ask questions and talk about your concerns.