How Cancer Is Staged
The stage
of a breast cancer describes the extent of the cancer in your body. Staging is usually based on
- the size of the tumor
- whether lymph nodes near the breast contain breast cancer
- whether the breast cancer has spread from the breast to other parts of the body
In general, the higher the stage, the larger the amount of cancer in your body. Doctors use these stages as one piece of information to help predict your chance of survival.
The stage of the breast cancer is determined by a system called the TNM staging system. These are the five major breast cancer stages:
Stage 0 breast cancer is noninvasive. This means the cancer cells are contained to the ducts of the breast. It is ductal carcinoma in situ, or DCIS.
Stage I breast cancers are invasive. They have grown outside the ducts or lobules of the breast. These cancers are 2 centimeters or smaller across and are not in any nearby lymph nodes.
Stage II and Stage III breast cancers are invasive. These are either larger breast tumors or some cancer is found in the lymph nodes near your breast, or both.
- Stage II cancers involve
- a tumor of any size that has not grown into the chest wall and muscles behind the breast or the skin of the breast, in combination with
- cancer in no lymph nodes, or cancer in up to three of the lymph nodes in the armpit, near the breast bone, or any combination of these
- a tumor of any size that has not grown into the chest wall
- Stage III cancers involve
- a tumor of any size, including one that has grown into the chest wall and muscles behind the breast or the skin of the breast, in combination with
- cancer in no lymph nodes or cancer in up to 10 or more lymph nodes in the armpit, near the collarbone, near the breast bone, or any combination of these
Stage IV or metastatic cancers are invasive. They have traveled away from the breast to other organs in the body, such as the bones, liver, lungs or brain.
The TNM System
After you receive a breast cancer diagnosis, your doctor may ask for radiology tests, more biopsies, a physical exam and more details from you about your symptoms. Using all this information, your doctor will assign a stage to the breast cancer using the American Joint Committee on Cancer (AJCC) TNM system.
The TNM system is one of the most widely used systems to describe the stages of breast cancer. Most cancer care teams use it as a standard way to describe how far the cancer has spread. Doctors use the TNM stage of the cancer to make decisions about which treatment is best for you.
Here is what each letter in “TNM” means:
- T stands for tumor. The T stage is determined by the size of the tumor and whether it has affected the skin over the breast or the muscle beneath the breast.
- N stands for (lymph) nodes. The N stage is determined either by
- the number of lymph nodes in the armpit, called axillary nodes, that have cancer
- the number of nodes near the breast bone in the center of the chest, called internal mammary nodes, that have cancer
- the number of nodes in the base of the neck near the collarbone, called supraclavicular nodes, that have cancer
- M stands for metastasis. The M stage is determined by whether the cancer has traveled from your breast and nearby lymph nodes to another area in your body
Each letter is also assigned a number to show the size of the original, or primary, tumor and how far the cancer has spread.
Here is a simple explanation of each stage in the TNM system:
The T (tumor) stages describe the original tumor.
- TX means the size of the tumor can’t be determined
- T0 means there is no evidence of the primary tumor
- Tis means the cancer is “in situ” (DCIS, LCIS or Paget disease of the breast with no tumor mass)
- T1 tumors are 2 centimeters or less across
- T2 tumors are larger than 2 centimeters but less than 5 centimeters across
- T3 tumors are larger than 5 centimeters across
- T4 cancers have spread into the chest wall or skin, or are inflammatory breast cancer
The N (node) stages describe whether or not the cancer is in your lymph nodes. N stage can be determined either by
- your doctor’s judgment based on your physical exam and radiology tests, called clinical stage
- your biopsy results from the lymph nodes, called pathologic stage
Your doctor looks at many factors to decide the N stage. You can get full details from the AJCC. But here are some general guidelines about N staging:
- NX means that it can’t be determined whether the cancer is in nearby lymph nodes
- N0 means cancer has not traveled to nearby lymph nodes
- N1 means cancer is in 1 to 3 armpit lymph nodes, in lymph nodes near the breast bone, or in both
- N2 means cancer is in 4 to 9 armpit lymph nodes, in the lymph nodes near the breast bone, or in both
- N3 means cancer is in 10 or more armpit lymph nodes, or in the lymph nodes near the collarbone, or in lymph nodes near the breast bone, or in some combination of these
The M (metastases) stage tells whether the cancer has traveled to a distant area in the body.
- MX means it can’t be determined whether or not the cancer has metastasized
- M0 means the cancer hasn’t metastasized
- M1 means the cancer has metastasized
Your doctor uses TNM results to give the cancer an overall stage, from stage 0 up to stage IV. For example, if your pathology report says the tumor is T3 N2 M0, it has spread to nearby lymph nodes but not to other parts of the body. It would be grouped as stage III.