Cancer
Breast Cancer
Diagnosis
Understanding the clinical staging of breast cancer
ByLauren Evoy Davis
Updated on September 06, 2024
Medically reviewed byMarla Anderson, MD
Table of Contents
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Table of Contents
Breast Cancer Tumor Size
TNM System
Stages
Other Staging Factors
After Clinical Staging
FAQ
Cancer stagingis the process of determining how muchcanceris within the body (tumor size) and if it has spread. For breast cancer, this might take the form of clinical (pre-surgical) staging or pathologic (surgical) staging.
Breast cancer is classified by stages. There are five stages of breast cancer, (stages 0, 1, 2, 3, and 4). Doctors use a specific classification system, known as the TNM (tumor, node, metastasis) system to stage breast cancer and guide treatment.
This article explains what is involved in clinical breast cancer staging and what the different stages mean. It also explains what to expect after the clinical stage has been established.
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Breast Cancer Tumor Size
Doctors usually measure the size of the tumor in centimeters (cm). Some common foods analogies can help to better understand tumor sizes:
- 1 cm is about the width of a pea
- 2 cm is about the size of a peanut
- 3 cm is about the size of a grape
- 4 cm is about the size of a walnut
- 5 cm is about the size of a lime
- 6 cm is about the size of an egg
- 7 cm is about the size of a peach
- 10 cm is about the size of a grapefruit
For the clinical staging of breast cancer, your cancer specialist (oncologist) may use one or more of the following imaging tools:
- Mammogram:This is an X-ray procedure specific to the breast.
- Breast ultrasound:This uses a non-invasive procedure that can visualize and measure a tumor using reflected sound waves.
- Breast magnetic resonance imaging (MRI): This uses powerful magnetic and radio waves to image soft tissue. It is typically employed when breast tissue is dense or a biopsy shows that the mass is larger than expected.
TNM System for Breast Cancer Staging
Breast cancer and most other solid tumor cancers are staged with a system called the TNM Classification of Malignant Tumors. The abbreviation "TNM" stands for the three characteristics used to determine the stage of cancer:
- Tumor size: This refers to the size and extent of the primary (main) tumor.
- Number of lymph nodes: This is the number and location of lymph nodes with cancer in them.
- Metastasis: This indicates whether or not cancer has spread (metastasized) from the primary tumor to other parts of the body.
Based on the findings, cancer is staged from 0 to 4, with 0 being the least advanced stage and 4 being the most advanced stage. The cancer stage directs the appropriate course of treatment and predicts the likely outcome (prognosis).
This includes determining whether a lumpectomy (the removal of the tumor) or a mastectomy (the removal of the tumor and breast) is needed.
Clinical vs. Pathologic Staging
Clinical breast cancer staging can help direct if a lumpectomy or mastectomy is most appropriate. But for the purpose of cancer diagnosis and treatment, pathologic breast cancer staging is considered the gold standard.
T Classification for Clinical Breast Cancer Staging
In the TNM system, tumor size plays a central role in clinical and pathologic staging. The extent to which the tumor has grown into surrounding tissues is also important.
Tumor size is categorized in the TNM system as follows:
| TX | Primary tumor cannot be assessed |
| T0 | No evidence of primary tumor |
| Tis | Carcinoma in situ (a group of abnormal cells that have not spread) |
| T-1 | Tumor is 2 cm or less across |
| T-2 | Tumor is greater than 2 cm and up to 5 cm across |
| T-3 | Tumor is greater than 5 cm across |
| T-4 | Tumor of any size growing into the chest wall or skin |
N Classification for Clinical Breast Cancer Staging
When you have breast cancer, the cancer cells can migrate through a network of lymphatic vessels to nearby lymph nodes. The lymph nodes nearest the tumor will almost invariably have more cancer cells than those further down the line.
The number and extent of lymph node involvement are central factors for the staging of breast cancer. This primarily involves axillary lymph nodes of the armpit, but may also involve supraclavicular lymph nodes around the collarbone and mediastinal lymph nodes around the breastbone.
For the clinical staging of breast cancer, your oncologist will palpate (physically touch) areas of skin nearest the tumor to feel for lumps. The clinical staging is ultimately based on the number, size, texture, and location of swollen lymph nodes.
| N-0 | No swollen lymph nodes are felt. |
| N-1 | One or more suspect lymph are felt around the armpit. |
| N-2 | Armpit lymph nodes are swollen, lumpy, and bunched together. |
| N-3 | Swollen lymph nodes are also found near the collarbone. |
Alternatively, your lymph nodes may be evaluated witha sentinel node biopsy. This is when one or two lymph nodes nearest the tumor are removed and directly inspected for cancer cells in the laboratory.
M Classification for Clinical Breast Cancer Staging
Metastasis is the extent to which cancer has spread beyond the primary (original) tumor. The M in breast cancer refers to spread to distant organs (liver, lung, bone) or the contralateral lymph node basins on the opposite side of the diagnosed breast cancer.
| M-0 | Imaging and physical exam has found no distant spread. |
| M-1 | The cancer has spread to other parts of the body. |
Procedures to confirm metastasis include a computed tomography (CT) scan and/or a positron emission tomography (PET) scan, both of which can pinpoint cancer cells in other parts of the body.
Where Can Breast Cancer Spread?
3:01
Breast Cancer Treatment Options
Stages of Breast Cancer
Breast cancer has five stages. Your stage is based on the TNM classification.
Stage 0
Stage 0 is used for precancer, also known as carcinoma in situ. This is when abnormal cells that look like cancer are seen under the microscope but are only found in the place where they first formed and therefore do not have the ability to spread to nearby lymph nodes or distant organs.
Stage 1
Stage 1means that cancer is small and is only in the breast tissue or possibly in the lymph nodes closest to the breath. There are two subcategories of stage 1 breast cancer:
Stage 1A:
- The tumor measures up to 2 cm.
AND - Cancer cells have not spread out of the breast into nearby lymph nodes.
Stage 1B:
- A small cluster of cancer cells measuring 0.2 to 2 millimeters (mm) is found in nearby lymph nodes.
- A tumor may or may not be present.
An Overview of Stage 1 Breast Cancer
Stage 2
Stage 2 is cancer that has become invasive and has spread into regional tissue. This stage also is divided into two subcategories:
Stage 2A:
- There is no tumor in the breast, but a cluster of cancer cells larger than 2 mm is found in either the axillary or supraclavicular lymph nodes
OR - The tumor is smaller than 2 cm and has spread to nearby lymph nodes.
OR - The tumor measures between 2 and 5 cm and hasn't spread to nearby lymph nodes.
Stage 2B:
- The tumor measures between 2 and 5 cm and a group of cancer cells between 0.2 and 2 mm are found in the axillary lymph nodes.
OR - The tumor measures 2 to 5 cm, and there is cancer in up to three axillary lymph nodes.
OR - The tumor measures larger than 5 cm, but there isn't any cancer in the axillary lymph nodes.
An Overview of Stage 2 Breast Cancer
Stage 3
Stage 3cancers are invasive. This stage is divided into three subcategories:
Stage 3A:
- Any size breast tumor (or no tumor) is present, and cancer has been found in four to nine axillary or mediastinal lymph nodes.
OR - The tumor is larger than 5 cm, and there is a small cluster of cancer cells between 0.2 and 2 mm in the lymph nodes.
OR - The tumor is larger than 5 cm, and cancer is found in up to three axillary or mediastinal lymph nodes.
Stage 3B:
- A tumor of any size has spread to the chest wall and/or skin with evidence of swelling or ulcers.
AND - Cancer has spread to up to nine axillary or mediastinal lymph nodes.
OR - There are skin changes suggestive of inflammatory breast cancer.
Stage 3C:
- There may be no tumor, or a tumor of any size has spread to the chest wall and/or skin.
AND - Cancer has spread to 10 or more axillary lymph nodes.
OR - Cancer has spread to supraclavicular lymph nodes above or below the collarbone.
OR - Cancer has spread to mediastinal lymph nodes.
An Overview of Stage 3 Breast Cancer
Stage 4
Stage 4is also called metastatic breast cancer. Rather than being confined to the breast and nearby lymph nodes, the cancer has traveled to other organs. It may also be a recurrence of breast cancer that has spread to other areas.
Common sites of metastases include the lungs, skin, bones, liver, brain, and distant lymph nodes.
An Overview of Stage 4 Breast Cancer
Breast Cancer Healthcare Provider Discussion Guide
Get our printable guide for your next healthcare provider's appointment to help you ask the right questions.
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Other Factors for Breast Cancer Staging
To better characterize the tumor you have, other tests may be performed in addition to the TNM classification. These contribute to the prognosis and treatment approach by establishing:
- Tumor grade: This is an examination of cancer cells to determine how aggressive (fast-growing) or indolent (slow-growing) they are.
- Hormone receptor status: These determine if you have receptors for the hormone estrogen and progesterone and whether certain targeted therapies can be used.
- HER2 status: HER2 is a protein found on some breast cancer cells that also act as a receptor for targeted drugs
After Clinical Staging
Biopsies and imaging studies give an approximate measurement of your tumor, but you need theactualtumor size in order to make the best treatment decisions.
This will involve either alumpectomyora mastectomy. By directly removing and examining the tumor, a surrounding margin of tissues, and nearby lymph nodes, the pathologist can provide all the information needed to accurately stage and grade your cancer.
Armed with this information, your oncologist can decide what other treatments are needed and when, including chemotherapy, radiation, hormonal therapy, or immunotherapy.
How Breast Cancer Is Treated
Summary
Breast cancer staging determines how muchcanceris within the body (tumor size) and if it has spread. Doctors use the TNM system to stage breast cancer and guide treatment. Additional testing may be done to determine the prognosis and best treatment approach.
After the staging process, a lumpectomy or mastectomy is performed. Additional treatment may include chemotherapy, radiation, hormonal therapy, or immunotherapy.
Frequently Asked Questions
How fast does breast cancer grow?
Volume doubling time estimates how fast breast cancer grows. This is the amount of time it takes for a tumor to double in size.Growth also depends on the type of breast cancer you have and whether you have been treated with hormone therapies.
Learn MoreHow Fast Does Breast Cancer Start, Grow, and Spread?
How do you tell if it’s a cyst or a tumor?
You will need to have a mammogram, CT (computed tomography) scan, or MRI. Additionally, you may need a biopsy to rule out cancer.
Learn MoreBenign and Malignant Breast Lumps
How do you know that a tumor is benign?
Benign tumors usually have a smooth, regular shape, whereas a cancerous tumor may have an uneven shape and appearance. A biopsy may be needed to rule out cancer.
7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
American Cancer Society. Breast cancer stages.
National Library of Medicine PDQ Cancer Information Summaries. Tumor sizes.
American Cancer Society. Imaging tests to find breast cancer.
American Joint Committee on Cancer. Cancer staging system.
American Cancer Society. Your Breast Pathology Report: Breast Cancer.
American Cancer Society. Cancer staging.
American Cancer Society. Breast cancer stages.
Additional Reading
Breastcancer.org 2018. Breast Cancer Stages.
National Cancer Institute 2015. Cancer Staging.
Susan G. Komen 2019. Breast Cancer Stages and Staging.
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By Lauren Evoy Davis
Evoy Davis is a health journalist based in Chesapeake Bay, Maryland. She is a member of the American Society of Healthcare Journalists.
Originally written byPam Stephan
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