Breast Cancer Stages
Doctors classify breast cancer as one of five stages based on the characteristics of the cancer.
How is a breast cancer stage determined?
The stage of a breast cancer is determined by the cancer’s characteristics, such as its size, whether or not it has hormone receptors, and its HER2 status. The stage of the cancer helps you and your doctor:
figure out your prognosis, the likely outcome of breast cancer treatment
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 Roman numeral from 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. Stage IV breast cancer is also called metastatic breast cancer.
Many research studies classify cancers as early-stage or advanced-stage. Early-stage cancers are stage 0, stage I, stage II, and stage III. Advanced-stage cancers are stage IV.
Your pathology report includes information that’s used to calculate the stage of the breast cancer — that is, whether it is limited to one area in the breast, or whether it has spread to healthy tissues inside the breast, to the lymph nodes under your arm or near your breastbone, or to other parts of the body. Your doctor begins to determine a cancer’s stage during surgery to remove it and looks at one or more of the underarm lymph nodes, which is where breast cancer tends to travel first. Your doctor also may order additional blood tests or imaging tests if there’s reason to believe the cancer has spread beyond the breast.
The TNM staging system
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 make sure that all doctors and treatment facilities are describing cancer the same way so that the treatment results of all people can be compared and understood.
In the past, a breast cancer’s stage was calculated based on three clinical characteristics: T (tumor size), N (whether there is cancer in the lymph nodes), and M (whether the cancer has spread to other parts of the body).
Numbers or letters after T, N, and M give more details about each characteristic. Higher numbers mean the cancer is more advanced.
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 cancer is in 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 don’t 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.
Expanded breast cancer staging guidelines
In 2018, the AJCC updated the breast cancer staging guidelines to add other characteristics to the T, N, M system to determine a cancer’s stage:
Tumor grade: a measurement of how different the cancer cells look compared to normal cells.
Estrogen and progesterone receptor status: Do the cancer cells have receptors for the hormones estrogen and progesterone?
HER2 status: are the cancer cells making too much of the HER2 protein?
Oncotype DX score, if the cancer is estrogen receptor-positive, HER2-negative, and there is no cancer in the lymph nodes.
“The updated guidelines mean that staging has caught up to how people are actually treated,” explained Elizabeth Mittendorf, MD, PhD, Rob and Karen Hale Distinguished Chair in Surgical Oncology and director of the Breast Immuno-Oncology Program at the Dana-Farber Cancer Institute. Mittendorf 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 gets a very different treatment plan than a woman diagnosed with stage II disease that is estrogen receptor-positive.”
In general, according to experts, the updated staging system classifies triple-negative breast cancer at a higher stage and classifies most hormone receptor-positive breast cancer at a lower stage. When cancer is classified at a lower stage, doctors call it down-staging.
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.
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.
Stage IV or metastatic?
The American Cancer Society (ACS) and the National Cancer Institute (NCI) both say that a cancer’s stage doesn’t change after a diagnosis. So, a person who was diagnosed in 2010 with stage II breast cancer and then had the cancer come back in the bones in 2015 technically is considered to have stage II breast cancer with metastatic recurrence to bone.
Still, this is not how most people — and even most oncologists — talk and think about cancer. If someone has breast cancer come back in a part of the body away from the breast, the person and doctors usually consider that cancer to be stage IV/metastatic.
The reason the ACS and NCI say that a cancer’s stage doesn’t change is so they can follow people over time and keep track of how many people diagnosed with a particular stage of cancer have a recurrence, as well as the type of recurrence. This allows the organizations to compile statistics on cancer outcomes.
“It’s confusing, to be sure,” says Brian Wojciechowski, MD, a medical oncologist with Alliance Cancer Specialists in Pennsylvania, who also serves as a Breastcancer.org medical adviser. “But for the purpose of individual patients and their personal journey and how we make treatment decisions, it doesn’t matter whether you have stage II with metastatic recurrence to bone or stage IV disease. In practice, the terms ‘metastatic’ and ‘stage IV’ are used interchangeably.”
At Breastcancer.org, we talk about breast cancer the way most doctors do. So, we do as the American Society of Clinical Oncology does and use the terms stage IV and metastatic interchangeably. We also consider a person who has a metastatic recurrence to have stage IV cancer.
What My Patients Are Asking: Explain the New Breast Cancer Staging Guidelines
Sep 17, 2019Stage 0 breast cancer
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.
Stage I breast cancer
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 cm 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 mm but not larger than 2 mm — are found in the lymph nodes or
there is a tumor in the breast that is no larger than 2 cm, and there are small groups of cancer cells — larger than 0.2 mm but not larger than 2 mm — in the lymph nodes
Still, if a breast cancer is initially classified as stage IB but also is estrogen receptor-positive or progesterone receptor-positive, doctors classify the cancer as stage IA because those two characteristics make it less aggressive.
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 don’t measure more than 1 mm.
Stage II breast cancer
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 mm) is found in one to three 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 cm or smaller and has spread to the axillary lymph nodes or
the tumor is larger than 2 cm but not larger than 5 cm and has not spread to the axillary lymph nodes
Still, the cancer will be down-staged if it :
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 less than 11
In general, stage IIB describes invasive breast cancer in which:
the tumor is larger than 2 cm but no larger than 5 cm; small groups of breast cancer cells — larger than 0.2 mm but not larger than 2 mm — are found in the lymph nodes or
the tumor is larger than 2 cm but no larger than 5 cm; cancer has spread to one to three axillary lymph nodes or to lymph nodes near the breastbone (found during a sentinel node biopsy) or
the tumor is larger than 5 cm but has not spread to the axillary lymph nodes
A stage IIB breast cancer will be down-staged if:
cancer is found in one to three axillary lymph nodes
it is HER2-positive
it is estrogen receptor-positive
it is progesterone receptor-positive
Stage III breast cancer
Stage III is divided into subcategories known as IIIA, IIIB, and IIIC.
In general, stage IIIA describes invasive breast cancer in which:
no tumor is found in the breast or the tumor may be any size; cancer is found in four to nine axillary lymph nodes or in the lymph nodes near the breastbone or
the tumor is larger than 5 cm; small groups of breast cancer cells (larger than 0.2 mm but not larger than 2 mm) are found in the lymph nodes or
the tumor is larger than 5 cm; cancer has spread to one to three axillary lymph nodes or to the lymph nodes near the breastbone
A stage IIIA breast cancer will be down-staged if it:
is grade 2
has spread to four to nine axillary lymph nodes
is estrogen receptor-positive
is progesterone receptor-positive
is HER2-positive
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 nine axillary lymph nodes or
may have spread to lymph nodes near the breastbone
A stage IIIB, breast cancer will be down-staged, even if it measures more than 5 cm across, if it:
is grade 3
has spread to four to nine axillary lymph nodes
is estrogen receptor-positive
is progesterone receptor-positive
is HER2-positive
Inflammatory breast cancer is considered at least stage IIIB.
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
A stage IIIC breast cancer will be down-staged, even if the cancer tumor measures any size, if it:
is grade 2
is estrogen receptor-positive
is progesterone receptor-positive
Stage IV breast cancer
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.
— Last updated on July 15, 2025 at 8:40 PM