Breast Cancer Stages
Breast cancer stage is usually expressed as a Roman numeral from 0 through IV. Stage 0 cancers are non-invasive: They remain within their original location, while stage IV cancers are invasive and have spread outside the breast to other parts of the body. Stage IV breast cancer is also called metastatic breast cancer. Some places use Arabic numbers — 0, 1, 2, 3, and 4 — to indicate cancer stage.
Doctors determine the stage of a breast cancer by considering the cancer’s characteristics , such as its size, grade, whether or not it has hormone receptors, and its HER2 status. Most of this information is in your pathology report.
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
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.
Breast cancer staging T categories
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; also called non-invasive cancer ).
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.
Breast cancer staging N categories
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 have cancer in them.
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.
Breast cancer staging M categories
The M category tells whether or not there’s evidence that the cancer has traveled to other parts of the body, called distant metastasis by doctors :
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: tells whether the cancer cells have receptors for the hormones estrogen and progesterone
HER2 status: reports whether the cancer cells are making too much of the HER2 protein
Oncotype DX Breast Score test (a type of genomic test): measures the likelihood of recurrence for certain cancers
“The updated guidelines mean that staging 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, the expanded 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.
Local, regional, and distant cancers
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, the chest, changes to the breast's shape, and lymph node enlargement that is visible or that your doctor can feel during an exam.
What My Patients Are Asking: Explain the New Breast Cancer Staging Guidelines
With guest Brian Wojciechowski, MD
Sep 17, 2019Diagnosis
Early-stage and advanced-stage cancers
Many research papers talk about early-stage and advanced-stage breast cancer. Nearly all doctors consider stage I and stage II cancers to be early-stage and stage IV cancers to be advanced-stage. Stage III cancers can be harder to classify. Some doctors consider stage IIIA and stage IIIB early-stage and stage IIIC advanced-stage, while others consider stage IIIB and IIIC advanced-stage. If you’re reading a research study that mentions early-stage or advanced-stage, you’ll need to check and see how the researchers defined the terms for that particular study.
What My Patients Are Asking: Explain the New Breast Cancer Staging Guidelines
With guest Brian Wojciechowski, MD
Sep 17, 2019Diagnosis
Early-stage and advanced-stage cancers
Many research papers talk about early-stage and advanced-stage breast cancer. Nearly all doctors consider stage I and stage II cancers to be early-stage and stage IV cancers to be advanced-stage. Stage III cancers can be harder to classify. Some doctors consider stage IIIA and stage IIIB early-stage and stage IIIC advanced-stage, while others consider stage IIIB and IIIC advanced-stage. If you’re reading a research study that mentions early-stage or advanced-stage, you’ll need to check and see how the researchers defined the terms for that particular study.
Stage 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's 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's 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:
there's no tumor in the breast, but cancer (larger than 2 mm) is found in one to three lymph nodes under the arm (axillary lymph nodes) 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
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 or
the tumor is larger than 5 cm but hasn't spread to the axillary lymph nodes
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
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
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
Stage II and stage III cancers may be down-staged (classified as a lower stage) depending on the grade of the cancer and the results of the hormone receptor and HER2 tests. Cancers are sometimes downstaged if the grade is 1 or 2, and if their estrogen receptor-positive, progesterone receptor-positive, and HER2-positive, though there may be exceptions.
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.
What’s the difference between metastatic and stage IV?
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 2020 with stage II breast cancer and then had the cancer come back in the bones in 2026 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 or metastatic — to them, the terms mean the same thing.
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.