Last Updated on March 18, 2020
Staging of breast cancer helps to describe the extent and spread of cancer within the body. It describes the location of cancer, how much cancer has grown, and whether it has spread to nearby or distant organs or lymph nodes.
Read more about Breast Cancer: Risk Factors, Classification, Diagnosis and Treatment
A battery of tests is used to find the stage of breast cancer. This includes a detailed examination of the excised surgical specimen containing the tumor, blood tests and imaging investigations comprising of CT scan, MRI, PET scan, etc.
Read more about MRI in Breast Cancer- Indications and Procedure
Why is Staging Done?
Staging is used for the following purposes
- To determine the prognosis or the likely outcome of the disease. The higher the stage, the worse is the prognosis.
- To decide on the best treatment options available.
- A lower stage will require less aggressive treatment as compared to a higher stage.
- For very advanced stage or metastatic cancer (when it has spread to distant organs), only palliative treatment may be offered.
- To determine if a patient with a particular stage will benefit from specific clinical trials.
Read more about Metastasis or Metastatic Disease
Difference between Pathologic Staging and Clinical Staging
The pathologic stage (or surgical stage) is determined by examining the surgical specimen removed during an operation. It gives an accurate assessment of the cancer stage.
If due to any reason, surgery cannot be carried out, a clinical-stage is assigned to cancer. This is based on the patient’s physical examination, findings on the small biopsy specimen, and imaging tests. It is less accurate as compared to the pathologic (surgical) stage.
Patients who receive neoadjuvant therapy (chemotherapy or radiotherapy before surgery to shrink tumor ) are not staged according to pathologic staging. This is because the therapy will change the original tumor size and lymph node status. So, staging in these patients is done by using information from physical exams, biopsies, and imaging done before neoadjuvant therapy, rather than information from the tumor removed during surgery.
TNM System of Staging
The staging system most commonly used for breast cancer is the TNM system provided by the American Joint Committee on Cancer (AJCC).
It uses the following three parameters to find the stage of breast cancer.
- Size or extent of the tumor (T): It tells about the size of the tumor and whether it has spread to nearby or adjacent areas.
- Spread to nearby lymph nodes (N): Whether cancer has spread to nearby lymph nodes? If yes, the number of lymph nodes involved?
- Spread to distant sites (M): Whether cancer has spread (metastasis) to distant organs such as the lungs, liver, bones or brain?
In January 2018, AJCC added the following additional parameters to determine the stage of breast cancer.
- Tumor grade (G): Whether the tumor is well, moderately or poorly differentiated (as determined by microscopic examination of the tumor)
- Grade 1 or well-differentiated: The cancer cells look like normal breast tissue. These tumors are slow-growing and have a better prognosis.
- Grade 2 or moderately differentiated. The cancer cells look less similar to normal breast cells. Their growth and prognosis are intermediate between grade 1 and grade 3 tumors.
- Grade 3 or poorly differentiated; The cancer cells look very different from normal breast cells. These tumors usually grow and spread rapidly and have the worst prognosis.
- Estrogen Receptor (ER) status: Whether the cancer cells have the protein called estrogen receptor?
- Progesterone Receptor (PR) status: Whether the cancer cells have the protein called progesterone receptor?
- Her2 status: Whether the cancer cells make too much of a protein called Her2?
Read more about Triple-Negative Breast Cancer
In addition, Oncotype Dx® Recurrence Score results may also be considered for staging in certain circumstances.
The information obtained from all the above parameters is combined to arrive at a stage grouping for the purpose of assigning an overall stage.
Including the information about tumor grade and ER, PR, and Her2 status has made breast cancer staging more accurate and prognostically more relevant since it takes into account the biology of the tumor. However, it has also made the staging more complex. It is best to ask the treating doctor about the significance of the specific stage.
Oncotype DX® and breast cancer stage
The Oncotype DX test is a genomic test that analyzes the activity of a group of genes to determine the likely behavior of cancer and its response to treatment.
Oncotype DX is part of breast cancer staging for some estrogen receptor-positive, lymph node-negative tumors.
The results of the Oncotype DX test, combined with other above-mentioned features of breast cancer, can help the doctor and patient make a more informed decision about the treatment (whether or not to have chemotherapy to treat early-stage, hormone-receptor-positive breast cancer or radiation therapy to treat DCIS, etc).
TNM Classification
Primary Tumor (T)
TX: The primary tumor can’t be assessed.
Tis: Carcinoma in situ (DCIS or LCIS).
Tis (Paget) refers to Paget disease of the nipple not associated with invasive carcinoma, DCIS or LCIS in the underlying breast.
T1: The tumor is ≤ 2 cm in greatest dimension.
T1 is further divided into:
- T1mi means the tumor is ≤ 0.1 cm in the greatest dimension.
- T1a means the tumor is > 0. 1 cm but ≤ 0.5 cm in greatest dimension.
- T1b means the tumor is > 0.5 cm but ≤ 1 cm in the greatest dimension.
- T1c means the tumor is > 1 cm but ≤ 2 cm in the greatest dimension.
T2: The tumor is > 2 cm but ≤ 5 cm in greatest dimension
T3: The tumor is > 5 cm in greatest dimension.
T4: The tumor may be of any size. In addition, there is a direct extension to the chest wall and/or to the skin (ulceration or skin nodules), not including the invasion of dermis alone.
T4 is divided into:
- T4a means the tumor has spread into the chest wall.
- T4b means the tumor has spread into the skin and the breast might be swollen.
- T4c means the tumor has spread to both the skin and the chest wall.
- T4d means inflammatory carcinoma – this is cancer in which the overlying skin is red, swollen and painful.
Read more about Inflammatory Breast Cancer: Clinical Features, Diagnosis, and Treatment
Image Credit: cancer.ca
Node (N)
Node (N) describes whether cancer has spread to the lymph nodes.
NX: The lymph nodes can’t be assessed (for example, if they were previously removed).
N0: There are no cancer cells in any nearby nodes.
Isolated tumor cells (ITCs) are small clusters of cancer cells < 0.2 mm, or a single tumor cell, or a cluster of fewer than 200 cells in one area of a lymph node. Lymph nodes containing only isolated tumor cells are not counted as positive lymph nodes.
N1: Cancer has spread to 1 to 3 axillary lymph nodes and/or the internal mammary lymph nodes.
N1 is further divided into:
- N1mi means one or more lymph nodes contain cancer cells called micrometastases which is > 0.2 mm but < 2 mm. Or the nodes contain more than 200 cancer cells.
- N1a means that cancer cells have spread to 1 to 3 axillary lymph nodes and at least one is larger than 2 mm.
- N1b means there are cancer cells in the ipsilateral internal mammary lymph nodes found with a sentinel node biopsy but the areas are too small to feel.
- N1c means there are cancer cells in 1 to 3 lymph nodes in the axillary and internal mammary lymph nodes but they are too small to feel.
N2: Cancer has spread to 4 to 9 axillary lymph nodes. Or it has spread to the internal mammary lymph nodes, but not the axillary lymph nodes.
N2 is divided into:
- N2a means there are cancer cells in 4-9 axillary lymph nodes. At least 1 tumor deposit > 2.0 mm.
- N2b means there are cancer cells in the internal mammary lymph nodes but no evidence of cancer in the axillary lymph nodes.
N3: Cancer has spread to ≥ 10 axillary lymph nodes. Or infraclavicular lymph nodes (located under the clavicle, or collarbone) or internal mammary lymph nodes. Cancer that has spread to the lymph nodes above the clavicle, called the supraclavicular lymph nodes, is also included in N3.
N3 is divided into:
- N3a means there are cancer cells in ≥ 10 axillary lymph nodes (at least 1 tumor deposit > 2.0 mm); or in infraclavicular lymph nodes.
- N3b means there are cancer cells in infraclavicular lymph nodes and axillary lymph nodes.
- N3c means there are cancer cells in ipsilateral supraclavicular lymph nodes.
It is important to know the exact number and location of lymph nodes involved by cancer as it helps to plan treatment.
Axillary lymph node removal is routinely performed during surgery for breast cancer. The pathologist examines and determines the number of axillary lymph nodes that contain cancer after they are removed during surgery.
The supraclavicular or internal mammary lymph nodes are not routinely removed during surgery. If there is cancer in these lymph nodes, treatments such as radiation therapy, chemotherapy or hormonal therapy are used to eliminate cancer.
Metastasis (M)
It describes whether cancer has spread to a different part of the body away from the primary site of origin.
MX: Distant spread cannot be assessed.
M0: cancer has not spread to a distant site.
cM0(i+): Small numbers of cancer cells are found in blood or bone marrow or lymph nodes far away from the breast. These cancer cells are found only by special laboratory tests
M1: Cancer has spread to a distant site like liver, lungs, brain or bone.
Staging of Breast Cancer
When describing the stage of breast cancer, sometimes doctors group them as follows:
In situ or non-invasive breast cancer: The cancer cells are limited to the duct or lobule from where they started (in-situ ductal and in-situ lobular cancer respectively) and have not grown into the nearby breast tissue. This is stage 0.
Early-stage breast cancer: The tumor is less than 5 cm in size and cancer has not spread to more than 3 lymph nodes. It includes stages 1A, 1B and 2A.
Locally advanced breast cancer: The tumor is more than 5 cm in size. In addition, cancer may have spread to the skin, the muscles of the chest wall or more than 3 nearby lymph nodes. It includes stages 2B, 3A, 3B and 3C. Inflammatory breast cancer is also included in this category.
Metastatic breast cancer: cancer has spread to distant parts of the body. It is stage 4.
Image Credit: jbcp.jo
Stage 0 (carcinoma in situ)
It includes either one of the following
- Ductal carcinoma in situ or DCIS: The cancer cells are limited to the breast ducts.
- Lobular carcinoma in situ or LCIS: The cancer cells are limited to the breast lobules.
- Paget’s disease of the breast in the absence of any underlying invasive carcinoma, DCIS or LCIS.
Stage 1A
The tumor is ≤ 2 cm in size.
Stage 1B
The tumor is ≤ 2 cm, or no tumor can be seen in the breast. A small number of cancer cells may be found in the lymph nodes (micrometastases). Each lymph node with cancer cells in it is no larger than 2 mm.
Stage 2A
The tumor is ≤ 2 cm, or no tumor can be seen in the breast. Cancer cells are found in 1 to 3 axillary lymph nodes or internal mammary lymph nodes or both.
Or the tumor is > 2 cm but < 5 cm in size.
Stage 2B
The tumor is > 2 cm but < 5 cm in size. Also, cancer has spread to 1 to 3 axillary lymph nodes, internal mammary lymph nodes or both areas.
Or the tumor is > 5 cm.
Stage 3A
The tumor is ≤ 5 cm, or no tumor can be seen in the breast. Cancer cells are found in 4 to 9 axillary lymph nodes, or in internal mammary lymph nodes but not in axillary lymph nodes.
Or the tumor is > 5 cm. Cancer has also spread to 1 to 9 axillary lymph nodes or to internal mammary lymph nodes. Or it may have spread to 1 to 3 axillary lymph nodes and internal mammary lymph nodes.
Stage 3B
The tumor has extended into the chest wall muscles or skin or both. Cancer may have also spread to 1 to 9 axillary lymph nodes or to internal mammary lymph nodes. Or it may have spread to 1 to 3 axillary lymph nodes and internal mammary lymph nodes.
Inflammatory breast cancer is also included in this stage.
Stage 3C
It may include any one of the following:
- Cancer has spread to 10 or more axillary lymph nodes or to infraclavicular lymph nodes.
- Cancer has spread to more than 3 axillary lymph nodes and internal mammary lymph nodes.
- Cancer has spread to supraclavicular lymph nodes.
Stage 4
Cancer has spread to distant parts of the body such as the bone, liver, lungs or brain. It is also known as metastatic breast cancer.
The table below lists the TNM classifications for each stage of breast cancer for people who have surgery as their first treatment.
When TNM is… | And Grade is… | And HER2 Status is… | And ER Status is… | And PR Status is… | Then the Clinical Prognostic Stage Group is… |
Tis N0 M0 | Any | Any | Any | Any | 0 |
T1* N0 M0
T0 N1mi M0 T1* N1mi M0 |
G1 | Positive | Positive | Positive | IA |
Negative | IA | ||||
Negative | Positive | IA | |||
Negative | IA | ||||
Negative | Positive | Positive | IA | ||
Negative | IA | ||||
Negative | Positive | IA | |||
Negative | IA | ||||
G2 | Positive | Positive | Positive | IA | |
Negative | IA | ||||
Negative | Positive | IA | |||
Negative | IA | ||||
Negative | Positive | Positive | IA | ||
Negative | IA | ||||
Negative | Positive | IA | |||
Negative | IB | ||||
G3 | Positive | Positive | Positive | IA | |
Negative | IA | ||||
Negative | Positive | IA | |||
Negative | IA | ||||
Negative | Positive | Positive | IA | ||
Negative | IA | ||||
Negative | Positive | IA | |||
Negative | IB | ||||
T0 N1**M0
T1*N1**M0 T2 N0 M0 |
G1 | Positive | Positive | Positive | IA |
Negative | IB | ||||
Negative | Positive | IB | |||
Negative | IIA | ||||
Negative | Positive | Positive | IA | ||
Negative | IB | ||||
Negative | Positive | IB | |||
Negative | IIA | ||||
G2 | Positive | Positive | Positive | IA | |
Negative | IB | ||||
Negative | Positive | IB | |||
Negative | IIA | ||||
Negative | Positive | Positive | IA | ||
Negative | IIA | ||||
Negative | Positive | IIA | |||
Negative | IIA | ||||
G3 | Positive | Positive | Positive | IA | |
Negative | IIA | ||||
Negative | Positive | IIA | |||
Negative | IIA | ||||
Negative | Positive | Positive | IB | ||
Negative | IIA | ||||
Negative | Positive | IIA | |||
Negative | IIA | ||||
T2 N1***M0
T3 N0 M0 |
G1 | Positive | Positive | Positive | IA |
Negative | IIB | ||||
Negative | Positive | IIB | |||
Negative | IIB | ||||
Negative | Positive | Positive | IA | ||
Negative | IIB | ||||
Negative | Positive | IIB | |||
Negative | IIB | ||||
G2 | Positive | Positive | Positive | IB | |
Negative | IIB | ||||
Negative | Positive | IIB | |||
Negative | IIB | ||||
Negative | Positive | Positive | IB | ||
Negative | IIB | ||||
Negative | Positive | IIB | |||
Negative | IIB | ||||
G3 | Positive | Positive | Positive | IB | |
Negative | IIB | ||||
Negative | Positive | IIB | |||
Negative | IIB | ||||
Negative | Positive | Positive | IIA | ||
Negative | IIB | ||||
Negative | Positive | IIB | |||
Negative | IIIA | ||||
T0 N2 M0
T1* N2 M0 T2 N2 M0 T3 N1*** M0 T3 N2 M0 |
G1 | Positive | Positive | Positive | IB |
Negative | IIIA | ||||
Negative | Positive | IIIA | |||
Negative | IIIA | ||||
Negative | Positive | Positive | IB | ||
Negative | IIIA | ||||
Negative | Positive | IIIA | |||
Negative | IIIA | ||||
G2 | Positive | Positive | Positive | IB | |
Negative | IIIA | ||||
Negative | Positive | IIIA | |||
Negative | IIIA | ||||
Negative | Positive | Positive | IB | ||
Negative | IIIA | ||||
Negative | Positive | IIIA | |||
Negative | IIIB | ||||
G3 | Positive | Positive | Positive | IIA | |
Negative | IIIA | ||||
Negative | Positive | IIIA | |||
Negative | IIIA | ||||
Negative | Positive | Positive | IIB | ||
Negative | IIIA | ||||
Negative | Positive | IIIA | |||
Negative | IIIC | ||||
T4 N0 M0
T4 N1*** M0 T4 N2 M0 Any T N3 M0 |
G1 | Positive | Positive | Positive | IIIA |
Negative | IIIB | ||||
Negative | Positive | IIIB | |||
Negative | IIIB | ||||
Negative | Positive | Positive | IIIA | ||
Negative | IIIB | ||||
Negative | Positive | IIIB | |||
Negative | IIIB | ||||
G2 | Positive | Positive | Positive | IIIA | |
Negative | IIIB | ||||
Negative | Positive | IIIB | |||
Negative | IIIB | ||||
Negative | Positive | Positive | IIIA | ||
Negative | IIIB | ||||
Negative | Positive | IIIB | |||
Negative | IIIC | ||||
G3 | Positive | Positive | Positive | IIIB | |
Negative | IIIB | ||||
Negative | Positive | IIIB | |||
Negative | IIIB | ||||
Negative | Positive | Positive | IIIB | ||
Negative | IIIC | ||||
Negative | Positive | IIIC | |||
Negative | IIIC | ||||
Any T Any N M1 | Any | Any | Any | Any | IV |
*T1 includes T1mi.
**N1 does not include N1mi. T1 N1mi M0 and T0 N1mi M0 cancers are included for prognostic staging with T1 N0 M0 cancers of the same prognostic factor status. ***N1 includes N1mi. T2, T3 and T4 cancers with N1mi are included for prognostic staging with T2 N1, T3 N1 and T4 N1, respectively. |
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The original source for this information is the AJCC Cancer Staging Manual, Eighth Edition (2017) published by Springer International Publishing. |
References
- American Joint Committee on Cancer. Breast. Amin MB, Edge S, Greene F, Byrd DR, Brookland RK, et al, eds. AJCC Cancer Staging Manual. 8th edition. New York, NY: Springer; 2017.