Primary Bone Cancer: Stages

The stage of a cancer is how much and how far the cancer has spread in your body. Your healthcare provider uses exams and imaging scans to find out the size of the cancer and where it is. They can also see if the cancer has grown into nearby tissues, 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.

For primary bone cancer (cancer that starts in the bones), the stage is based on where the cancer is in the body, the size of the tumor, and the grade of the cancer.

The grade of the cancer describes how quickly the cancer is likely to grow and spread. It's based on how much the cancer cells from a biopsy look like normal cells under the microscope. Primary bone cancer has three grades. Low-grade (grade 1) cancers look more like normal bone cells. These cancers are usually slow-growing and less likely to grow and spread. High-grade (grade 2 or 3) cancers look very abnormal. They are more likely to grow quickly and spread.

The stage of a bone cancer is based on the grade, the size of the main tumor, and if it has spread outside the bone. Most bone cancers are grouped into one of four stages. The stages can have a value of Roman numerals I, II, III, and IV (1 through 4). The higher the number, the more advanced your cancer is. 

• Stage I. The cancer is only in the bone. But it may be in more than one place in the same bone. It's low-grade, or the grade hasn't been determined. (This may be written as grade X.)

• Stage II. The cancer is only in one place in one bone but it's high-grade.

• Stage III. The cancer is in more than one place in the same bone. It's only in the bone, and is high-grade.

• Stage IV. The cancer has spread outside the bone where it started to other bones or to the lungs, liver, or brain. It can be low- or high-grade.

Stage I and II cancers can be further divided (into A and B) based on the size of the tumor. Stage IV cancers can be further divided (into A and B) based on where the cancer has spread.

Once your cancer is staged, your healthcare provider will talk with you about what the stage means for you. Make sure to ask questions and talk about your concerns. Staging can be complex. Ask your provider to explain it in a way you understand.