Breast Cancer Stages

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The stage of a breast cancer is determined by the cancer’s characteristics, such as how large it is and whether or not it has hormone receptors. The stage of the cancer helps you and your doctor:

  • figure out your prognosis, the likely outcome of the disease
  • decide on the best treatment options for you
  • determine if certain clinical trials may be a good option for you

Breast cancer stage is usually expressed as a number on a scale of 0 through IV — with stage 0 describing non-invasive cancers that remain within their original location and stage IV describing invasive cancers that have spread outside the breast to other parts of the body.

How a breast cancer’s stage is determined

Your pathology report will include information that is used to calculate the stage of the breast cancer — that is, whether it is limited to one area in the breast, or it has spread to healthy tissues inside the breast or to other parts of the body. Your doctor will begin to determine this during surgery to remove the cancer and look at one or more of the underarm lymph nodes, which is where breast cancer tends to travel first. He or she also may order additional blood tests or imaging tests if there is reason to believe the cancer might have spread beyond the breast.

The breast cancer staging system, called the TNM system, is overseen by the American Joint Committee on Cancer (AJCC). The AJCC is a group of cancer experts who oversee how cancer is classified and communicated. This is to ensure that all doctors and treatment facilities are describing cancer in a uniform way so that the treatment results of all people can be compared and understood.

In the past, stage number was calculated based on just three clinical characteristics, T, N, and M:

  • the size of the cancer tumor and whether or not it has grown into nearby tissue (T)
  • whether cancer is in the lymph nodes (N)
  • whether the cancer has spread to other parts of the body beyond the breast (M)

Numbers or letters after T, N, and M give more details about each characteristic. Higher numbers mean the cancer is more advanced. Jump to more detailed information about the TNM system.

In 2018, the AJCC updated the breast cancer staging guidelines to add other cancer characteristics to the T, N, M system to determine a cancer’s stage:

Adding information about tumor grade, hormone-receptor status, HER2 status, and possibly Oncotype DX test results has made determining the stage of a breast cancer more complex, but also more accurate.

“The updated guidelines mean that staging is now catching up to how people are actually treated,” explained Elizabeth Mittendorf, M.D., Ph.D., Rob and Karen Hale Distinguished Chair in Surgical Oncology and director of the Breast Immuno-Oncology Program at the Dana-Farber Cancer Institute, who served on the expert panel that wrote the updated guidelines. “When developing a treatment plan, doctors always consider tumor grade, hormone-receptor status, HER2 status, and the Oncotype DX score, if applicable. So, a woman diagnosed with stage II disease that is triple-negative [estrogen-receptor-negative, progesterone-receptor-negative, and HER2-negative] will have a very different treatment plan than a woman diagnosed with stage II disease that is estrogen-receptor-positive. The staging guidelines now take into account what doctors have been doing all along.”

In general, according to experts, the new staging system classifies triple-negative breast cancer (estrogen-receptor-negative, progesterone-receptor-negative, and HER2-negative) at a higher stage and classifies most hormone-receptor-positive breast cancer at a lower stage.

You also may see or hear certain words used to describe the stage of the breast cancer:

  • Local: The cancer is confined within the breast.
  • Regional: The lymph nodes, primarily those in the armpit, are involved.
  • Distant: The cancer is found in other parts of the body as well.

Sometimes doctors use the term “locally advanced” or “regionally advanced” to refer to large tumors that involve the breast skin, underlying chest structures, changes to the breast's shape, and lymph node enlargement that is visible or that your doctor can feel during an exam.

Jump to a specific breast cancer stage to learn more:

The updated AJCC breast cancer staging guidelines have made determining the stage of a cancer a more complicated but accurate process. So, the characteristics of each stage below are somewhat generalized. To see all the possible characteristics of each stage, you can review the AJCC Breast Cancer Staging Guidelines (PDF) online.

Stage 0

Stage 0 is used to describe non-invasive breast cancers, such as DCIS (ductal carcinoma in situ). In stage 0, there is no evidence of cancer cells or non-cancerous abnormal cells breaking out of the part of the breast in which they started, or getting through to or invading neighboring normal tissue.

Learn about what treatments you can generally expect for stage 0 in the Options by Cancer Stage: Stage 0 page in Planning Your Treatment.

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Stage I

Stage I describes invasive breast cancer (cancer cells are breaking through to or invading normal surrounding breast tissue) Stage I is divided into subcategories known as IA and IB.

In general, stage IA describes invasive breast cancer in which:

  • the tumor measures up to 2 centimeters and
  • the cancer has not spread outside the breast; no lymph nodes are involved

In general, stage IB describes invasive breast cancer in which:

  • there is no tumor in the breast; instead, small groups of cancer cells — larger than 0.2 millimeter but not larger than 2 millimeters — are found in the lymph nodes or
  • there is a tumor in the breast that is no larger than 2 centimeters, and there are small groups of cancer cells — larger than 0.2 millimeter but not larger than 2 millimeters — in the lymph nodes

Still, if the cancer is estrogen-receptor-positive or progesterone-receptor-positive, it is likely to be classified as stage IA.

Microscopic invasion is possible in stage I breast cancer. In microscopic invasion, the cancer cells have just started to invade the tissue outside the lining of the duct or lobule, but the invading cancer cells can't measure more than 1 millimeter.

Learn about what treatments you can generally expect for stage IA and IB in the Options by Cancer Stage: Stage IA and IB page in Planning Your Treatment.

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Stage II

Stage II is divided into subcategories known as IIA and IIB.

In general, stage IIA describes invasive breast cancer in which:

  • no tumor can be found in the breast, but cancer (larger than 2 millimeters) is found in 1 to 3 axillary lymph nodes (the lymph nodes under the arm) or in the lymph nodes near the breast bone (found during a sentinel node biopsy) or
  • the tumor measures 2 centimeters or smaller and has spread to the axillary lymph nodes or
  • the tumor is larger than 2 centimeters but not larger than 5 centimeters and has not spread to the axillary lymph nodes

Still, if the cancer tumor measures between 2 and 5 centimeters and:

  • has not spread to the lymph nodes or parts of the body away from the breast
  • is HER2-negative
  • is hormone-receptor-positive

it will likely be classified as stage IB.

Similarly, if the cancer tumor measures between 2 and 5 centimeters and:

  • has not spread to the lymph nodes
  • is HER2-negative
  • is estrogen-receptor-positive
  • is progesterone-receptor-negative
  • has an Oncotype DX Recurrence Score of 9

it will likely be classified as stage IA.

In general, stage IIB describes invasive breast cancer in which:

  • the tumor is larger than 2 centimeters but no larger than 5 centimeters; small groups of breast cancer cells — larger than 0.2 millimeter but not larger than 2 millimeters — are found in the lymph nodes or
  • the tumor is larger than 2 centimeters but no larger than 5 centimeters; cancer has spread to 1 to 3 axillary lymph nodes or to lymph nodes near the breastbone (found during a sentinel node biopsy) or
  • the tumor is larger than 5 centimeters but has not spread to the axillary lymph nodes

Still, if the cancer tumor measures between 2 and 5 centimeters and:

  • cancer is found in 1 to 3 axillary lymph nodes
  • is HER2-positive
  • estrogen-receptor-positive
  • progesterone-receptor-positive

it will likely be classified as stage IB.

Learn about what treatments you can generally expect for stage IIA and IIB in the Options by Cancer Stage: Stage IIA and IIB page in Planning Your Treatment.

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Stage III

Stage III is divided into subcategories known as IIIA, IIIB, and IIIC.

In general, stage IIIA describes invasive breast cancer in which either:

  • no tumor is found in the breast or the tumor may be any size; cancer is found in 4 to 9 axillary lymph nodes or in the lymph nodes near the breastbone (found during imaging tests or a physical exam) or
  • the tumor is larger than 5 centimeters; small groups of breast cancer cells (larger than 0.2 millimeter but not larger than 2 millimeters) are found in the lymph nodes or
  • the tumor is larger than 5 centimeters; cancer has spread to 1 to 3 axillary lymph nodes or to the lymph nodes near the breastbone (found during a sentinel lymph node biopsy)

Still, if the cancer tumor measures more than 5 centimeters across and:

  • is grade 2
  • cancer is found in 4 to 9 axillary lymph nodes
  • is estrogen-receptor-positive
  • is progesterone-receptor-positive
  • is HER2-positive

it will likely be classified as stage IB.

In general, stage IIIB describes invasive breast cancer in which:

  • the tumor may be any size and has spread to the chest wall and/or skin of the breast and caused swelling or an ulcer and
  • may have spread to up to 9 axillary lymph nodes or
  • may have spread to lymph nodes near the breastbone

Still, if the cancer tumor measures more than 5 centimeters across and:

  • is grade 3
  • cancer is found in 4 to 9 axillary lymph nodes
  • is estrogen-receptor-positive
  • is progesterone-receptor-positive
  • is HER2-positive

it will likely be classified as stage IIA.

Inflammatory breast cancer is considered at least stage IIIB. Typical features of inflammatory breast cancer include:

  • reddening of a large portion of the breast skin
  • the breast feels warm and may be swollen
  • cancer cells have spread to the lymph nodes and may be found in the skin

In general, stage IIIC describes invasive breast cancer in which:

  • there may be no sign of cancer in the breast or, if there is a tumor, it may be any size and may have spread to the chest wall and/or the skin of the breast and
  • the cancer has spread to 10 or more axillary lymph nodes or
  • the cancer has spread to lymph nodes above or below the collarbone or
  • the cancer has spread to axillary lymph nodes or to lymph nodes near the breastbone

Still, if the cancer tumor measures any size and:

  • is grade 2
  • is estrogen-receptor-positive
  • is progesterone-receptor-positive
  • is HER2-positive or negative

it will likely be classified as stage IIIA.

Learn about what treatments you can generally expect for stage IIIA and operable IIIC in the Options by Cancer Stage: Stage IIIA and Operable IIIC page in Planning Your Treatment.

Learn about what treatments you can generally expect for stage IIIB and inoperable IIIC in the Options by Cancer Stage: Stage IIIB and Inoperable IIIC page in Planning Your Treatment.

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Stage IV

Stage IV describes invasive breast cancer that has spread beyond the breast and nearby lymph nodes to other organs of the body, such as the lungs, distant lymph nodes, skin, bones, liver, or brain.

You may hear the words “advanced” and “metastatic” used to describe stage IV breast cancer. Cancer may be stage IV at first diagnosis, called “de novo” by doctors, or it can be a recurrence of a previous breast cancer that has spread to other parts of the body.

Learn about what treatments you can generally expect for stage IV in the Options by Cancer Stage: Stage IV page in Planning Your Treatment.

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More information about the TNM staging system

The T (size) category describes the original (primary) tumor:

  • TX means the tumor can't be assessed.
  • T0 means there isn't any evidence of the primary tumor.
  • Tis means the cancer is "in situ" (the tumor has not started growing into healthy breast tissue).
  • T1, T2, T3, T4: These numbers are based on the size of the tumor and the extent to which it has grown into neighboring breast tissue. The higher the T number, the larger the tumor and/or the more it may have grown into the breast tissue.

The N (lymph node involvement) category describes whether or not the cancer has reached nearby lymph nodes:

  • NX means the nearby lymph nodes can't be assessed, for example, if they were previously removed.
  • N0 means nearby lymph nodes do not contain cancer.
  • N1, N2, N3: These numbers are based on the number of lymph nodes involved and how much cancer is found in them. The higher the N number, the greater the extent of the lymph node involvement.

The M (metastasis) category tells whether or not there is evidence that the cancer has traveled to other parts of the body:

  • MX means metastasis can't be assessed.
  • M0 means there is no distant metastasis.
  • M1 means that distant metastasis is present.

For more detailed information on the TNM staging system, visit the American Cancer Society’s section on breast cancer staging.

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