Breast Cancer: Stages

Approved by the Cancer.Net Editorial Board, 04/2017

ON THIS PAGE: You will learn about how doctors describe a cancer’s growth or spread. This is called the stage. Use the menu to see other pages.

Staging is a way of describing where the cancer is located, how much the cancer has grown, and if or where it has spread. Doctors use diagnostic tests to find out the cancer's stage, so staging may not be complete until all the tests are finished. Knowing the stage helps the doctor to decide what kind of treatment is best and can help predict a patient's prognosis, which is the chance of recovery. There are different stage descriptions for different types of cancer.

TNM staging system

The most commonly used tool that doctors use to describe the stage is the TNM system. Doctors use the results from diagnostic tests and scans to answer these questions:

  • Tumor (T): How large is the primary tumor? Where is it located?

  • Node (N): Has the tumor spread to the lymph nodes? If so, where and how many? 

  • Metastasis (M): Has the cancer metastasized to other parts of the body? If so, where and how much?

The results are combined to determine the stage of cancer for each person. There are 5 stages: stage 0 (zero), which is noninvasive ductal carcinoma in situ (DCIS), and stages I through IV (1 through 4), which are used for invasive breast cancer. The stage provides a common way of describing the cancer, so doctors can work together to plan the best treatments.

There are 2 types of TNM staging for breast cancer. First, the clinical stage is based on the results of tests done before surgery, which may include a physical examination, mammogram, ultrasound, and MRI scans. Then, the pathologic stage is assigned based on the pathology results from the breast tissue and any lymph nodes removed during surgery. It is usually determined several days after surgery. In general, more importance is placed on the pathologic stage than the clinical stage.

Here are more details on each part of the TNM system for breast cancer:

Tumor (T)

Using the TNM system, the “T” plus a letter or number (0 to 4) is used to describe the size and location of the tumor. Some stages are divided into smaller groups that help describe the tumor in even more detail. Specific tumor stage information in listed below.

TX: The primary tumor cannot be evaluated.

T0 (T plus zero): There is no evidence of cancer in the breast.

Tis: Refers to carcinoma in situ. The cancer is confined within the ducts or lobules of the breast tissue and has not spread into the surrounding tissue of the breast. There are 2 types of breast carcinoma in situ:

  • Tis (DCIS): DCIS is a noninvasive cancer, but if not removed it can develop into an invasive breast cancer later. DCIS means that cancer cells have been found in breast ducts and have not spread past the layer of tissue where they began.

  • Tis (Paget’s): Paget’s disease of the nipple is a rare form of early, noninvasive cancer that is only in the skin cells of the nipple. Sometimes Paget’s disease is associated with another, invasive breast cancer. If there is another invasive breast cancer, it is classified according to the stage of the invasive tumor.

T1: The tumor in the breast is 20 millimeters (mm) or smaller in size at its widest area. This is a little less than an inch. This stage is then broken into 4 substages depending on the size of the tumor:

  • T1mi is a tumor that is 1mm or smaller

  • T1a is a tumor that is larger than 1 mm but 5 mm or smaller

  • T1b is a tumor that is larger than 5 mm but 10 mm or smaller

  • T1c is a tumor that is larger than 10 mm but 20 mm or smaller

T2: The tumor is larger than 20 mm but not larger than 50 mm.

T3: The tumor is larger than 50 mm.

T4: The tumor falls into 1 of the following groups:

  • T4a means the tumor has grown into the chest wall.

  • T4b is when the tumor has grown into the skin.

  • T4c is cancer that has grown into the chest wall and the skin.

  • T4d is inflammatory breast cancer.

Node (N)

The “N” in the TNM staging system stands for lymph nodes. Regional lymph nodes include:

  • Lymph nodes located under the arm, called the axillary lymph nodes

  • Above and below the collarbone

  • Under the breastbone, called the internal mammary lymph nodes

Lymph nodes in other parts of the body are called distant lymph nodes. As explained above, if the doctor evaluates the lymph nodes before surgery, based on other tests and/or a physical examination, a letter “c” for “clinical” staging is placed in front of the “N.” If the doctor evaluates the lymph nodes after surgery, which is a more accurate assessment, a letter “p” for “pathologic” staging is placed in front of the “N.” The information below describes the pathologic staging.

NX: The lymph nodes cannot be evaluated.

N0: No cancer was found in the lymph nodes. Or only areas of cancer smaller than 0.2 mm are in the lymph nodes.

N1: The cancer within the lymph nodes falls into 1 of the following groups:

  • N1mi is when there is cancer in the axillary lymph nodes that is larger than 0.2 mm but smaller than 2 mm in size. This is often called a micrometastasis.

  • N1a is when there is cancer in 1 to 3 axillary lymph nodes and at least 1 of the lymph nodes is larger than 2mm. This is called a macrometastasis. This group can include positive internal mammary lymph nodes if they are found during a sentinel lymph node procedure.

  • N1b is when there is cancer larger than 0.2 mm in the internal mammary lymph nodes on the same side of the body as the main tumor.

  • N1c includes N1and N1b together.

N2: The cancer within the lymph nodes falls into 1 of the following groups:

  • N2a is when the cancer has spread to 4 to 9 axillary lymph nodes, with at least 1 larger than 2 mm.

  • N2b is when the cancer has spread to internal mammary lymph nodes without spread to the axillary nodes.

N3: The cancer falls within 1 of the following groups:

  • N3a is when the cancer has spread to 10 or more lymph nodes under the arm, with at least 1 larger than 2mm. Or it has spread to lymph nodes located under the clavicle, or collarbone.

  • N3b includes N1a or N1b, along with cancer in the internal mammary lymph nodes seen on imaging tests.

  • N3c is when the cancer has spread to the lymph nodes located above the clavicle, called the supraclavicular lymph nodes.

If there is cancer in the lymph nodes, knowing how many lymph nodes are involved and where they are helps doctors to plan treatment. The pathologist can find out the number of axillary lymph nodes that contain cancer after they are removed during surgery. It is not common to remove the supraclavicular or internal mammary lymph nodes during surgery. If there is cancer in these lymph nodes, treatment other than surgery, such as radiation therapy, chemotherapy, and hormonal therapy are used.

Metastasis (M)

The “M” in the TNM system indicates whether the cancer has spread to other parts of the body, called distant metastasis. This is no longer considered early-stage or locally advanced cancer. For more information on metastatic breast cancer, see the Guide to Metastatic Breast Cancer.

MX: Distant spread cannot be evaluated.

M0: The disease has not metastasized.

M0 (i+): There is no clinical or radiographic evidence of distant metastases. Microscopic evidence of tumor cells is found in the blood, bone marrow, or other lymph nodes that are no larger than 0.2 mm.

M1: There is evidence of metastasis to another part of the body, meaning there are breast cancer cells growing in other organs.

Cancer stage grouping

Doctors assign the stage of the cancer by combining the T, N, and M classifications. They also use other factors, such as tumor grade and the results of ER/PR and HER2 testing to determine the stage and your prognosis (see Diagnosis).

Most patients are anxious to learn the exact stage of the cancer. Your doctor will generally confirm the stage of the cancer when the testing after surgery is finalized, usually about 5 to 7 days after surgery. When systemic or whole body treatment is given before surgery, called neoadjuvant therapy, the stage of the cancer is primarily determined clinically. Doctors may refer to stage I to stage IIA cancer as early stage, and stage IIB to stage III as locally advanced.

Stage 0: Stage zero (0) describes disease that is only in the ducts and lobules of the breast tissue and has not spread to the surrounding tissue of the breast. It is also called noninvasive cancer (Tis, N0, M0).

Stage IA: The tumor is small, invasive, and has not spread to the lymph nodes (T1, N0, M0).

Stage IB: Cancer has spread only to the lymph nodes and is larger than 0.2 mm but less than 2 mm in size. There is either no evidence of a tumor in the breast or the tumor in the breast is 20 mm or smaller (T0 or T1, N1mi, M0).

Stage IIA: Any 1 of these conditions:

  • There is no evidence of a tumor in the breast, but the cancer has spread to the axillary lymph nodes. It has not spread to distant parts of the body. (T0, N1, M0).

  • The tumor is 20 mm or smaller and has spread to the axillary lymph nodes (T1, N1, M0).

  • The tumor is larger than 20 mm but not larger than 50 mm and has not spread to the axillary lymph nodes (T2, N0, M0).

Stage IIB: Either of these conditions:

  • The tumor is larger than 20 mm but not larger than 50 mm and has spread to 1 to 3 axillary lymph nodes (T2, N1, M0).

  • The tumor is larger than 50 mm but has not spread to the axillary lymph nodes (T3, N0, M0).

Stage IIIA: The cancer of any size has spread to 4 to 9 axillary lymph nodes or to internal mammary lymph nodes. It has not spread to other parts of the body (T0, T1, T2 or T3, N2, M0). Stage IIIA may also be a tumor larger than 50 mm that has small areas of cancer in the lymph nodes (T3, N1, M0).

Stage IIIB: The tumor has spread to the chest wall or caused swelling or ulceration of the breast or is diagnosed as inflammatory breast cancer. It may or may not have spread to the axillary or internal mammary lymph nodes. It has not spread to other parts of the body (T4; N0, N1 or N2; M0).

Stage IIIC: A tumor of any size that has spread to 10 or more axillary lymph nodes, the internal mammary lymph nodes, and/or the lymph nodes under the collarbone. It has not spread to other parts of the body (any T, N3, M0).

Stage IV (metastatic): The tumor can be any size and has spread to other organs, such as the bones, lungs, brain, liver, distant lymph nodes, or chest wall (any T, any N, M1). Metastatic cancer found when the cancer is first diagnosed occurs about 5% to 6% of the time. This may be called de novo metastatic breast cancer. Most commonly, metastatic breast cancer is found after a previous diagnosis of early breast cancer. Learn more about metastatic breast cancer.

Recurrent: Recurrent cancer is cancer that has come back after treatment, and can be described as local, regional, and/or distant. If the cancer does return, there will be another round of tests to learn about the extent of the recurrence. These tests and scans are often similar to those done at the time of the original diagnosis.

Used with permission of the American College of Surgeons, Chicago, Illinois. The original and primary source for this information is the AJCC Cancer Staging Manual, Eighth Edition (2017) published by Springer International Publishing.

Information about the cancer’s stage will help the doctor recommend a specific treatment plan. The next section in this guide is Treatment Options. You may use the menu to choose a different section to read in this guide.