Tests are performed to identify whether cancer cells have spread within the breast or to other parts of the body after a person is found to have a malignant tumour or is diagnosed with breast cancer.
Staging is the technique used to determine whether cancer has spread only within the breast or other body areas. The data acquired during the staging procedure determines the disease’s Stage. It is critical to understand the Stage of selecting a treatment course. The outcomes of some of the tests used to identify breast cancer are also used to categorise the severity of the condition.
The American Joint Committee on Cancer (AJCC) released new staging recommendations for breast cancer on January 1, 2018.
Identifying the Stage of Breast Cancer
The primary tumour’s size and location, the spread of the disease to neighbouring lymph nodes or other body regions, the tumour grade, and the presence or absence of specific biomarkers are considered when determining the Stage of breast cancer.
The breast cancer stage is determined by combining the TNM system, the grading system, and the biomarker status.
TNM System
The TNM system describes the primary tumour’s size and cancer’s ability to spread to nearby lymph nodes or other body regions.
TNM translates to:
- T stands for tumour. The tumour’s dimensions and placement.
- Lymph Node, or N. the number and location of lymph nodes affected by malignancy.
- M is for metastasis. The growth of cancer in additional bodily regions.
Grading System
The tumour grading system indicates how quickly a breast tumour is expected to grow and spread.
Biomarker Test
To ascertain which receptors breast cancer cells possess, biomarker testing is used.
Breast Cancer Tests
The tests and methods listed below may also be employed during the staging process:
- Sentinel lymph node biopsy: Surgically removing the sentinel lymph node. A collection of lymph nodes, starting with the sentinel lymph node, initially receive lymphatic outflow from the primary tumour. It is the first lymph node that the primary tumour’s primary tumour will most likely spread to. Near the tumour, radioactive material or the blue dye may be injected. The material or dye travels to the lymph nodes via the lymphatic ducts. It is removed once the first lymph node is exposed to the chemical or dye. A pathologist examines the tissue under a microscope to check for cancer cells. It might not be necessary to remove any more lymph nodes if cancer cells are not discovered. A sentinel lymph node may occasionally be discovered in multiple groups of nodes.
- X-ray reveals the internal organs and bones of the chest. An X-ray is a specific energy beam that can photograph inside organs by passing through the body and onto film.
- A sequence of detailed images of different body parts is created using the CT scan (a CAT scan). An X-ray machine and a computer are connected to create the images. A dye may be ingested or injected into a vein to make the organs or tissues more visible. This process is also known as computerised axial, computed, and computed tomography.
- Bone scan: A test to see if the bone has cells that divide quickly, such as cancer cells. A very tiny quantity of the radioactive substance is injected into a vein and enters the bloodstream. A scanner can find the radioactive substance that accumulates in the cancerous bones.
- The body’s malignant tumour cells can be located with a PET or positron emission tomography scan. A vein receives a tiny injection of radioactive glucose (sugar). The PET scanner spins around the body to provide an image of the areas of the body where glucose is being utilised. Since malignant tumour cells are more active and absorb more glucose than healthy cells, they appear brighter in the image.
Metastasis
Cancer can spread across the body in three different ways. Cancer can spread through blood, lymphatics, and tissue:
- Tissue. Cancer grows into neighbouring locations as it spreads from its original location.
- System of lymph. The lymphatic system is where cancer spreads from its original site. The lymphatic vessels serve as cancer’s conduit to other body regions.
- Blood. By entering the bloodstream, cancer spreads from the site of its initiation. The malignancy reaches other bodily parts via the blood arteries.
From the initial site of cancer, it may spread to other body parts. Metastasis is the medical term for the spread of cancer to another area of the body. Cancerous cells separate from the original tumour, where they first appeared, and move through the lymphatic or circulatory systems.
- System of lymph. The cancer spreads to another body area after entering the lymphatic system and moving through lymphatic vessels.
- Blood. Cancer spreads to another area of the body after entering the blood and passing through blood vessels.
The main tumour’s malignancy also spread to the metastatic tumour. For Example, those breast cancer cells that spread to the bone are indeed breast cancer cells. Not bone cancer, but metastatic breast cancer is the illness.
Breast Cancer Stage Groups
The size and location of the main tumour, the spread of the disease to neighbouring lymph nodes or other body regions, the tumour grade, and the presence or absence of specific biomarkers are considered when determining the Stage of breast cancer. Knowing your breast cancer Stage is crucial for choosing the best course of action and comprehending your prognosis.
There are three different breast cancer stage categories:
- All patients are first given a stage using the clinical prognostic Stage based on their medical history, physical examination, imaging tests (if any), and biopsies. The TNM system, tumour grade, and biomarker status represent the clinical prognostic Stage (ER, PR, HER2). Mammography or ultrasound is utilised during clinical staging to examine the lymph nodes for cancerous lesions.
- When surgery is the first course of treatment for a patient, the Pathological Prognostic Stage is used. The pathological prognostic Stage is determined based on all clinical data, biomarker status, and laboratory test findings from the breast tissue and lymph nodes retrieved following surgery.
- The anatomic Stage is determined by the TNM system’s descriptions of the size and distribution of the tumour. In regions of the world without access to biomarker testing, the Anatomic Stage is used. In the US, it is not practised.
TNM System
The TNM classification system describes the size of the primary tumour and cancer spread to nearby lymph nodes or other body parts.
The TNM system describes breast cancer tumours as follows:
A tumour (T) (T). The tumour’s size and location.
- TX: The primary tumour cannot be evaluated.
- T0: No evidence of a primary breast tumour.
- This is a carcinoma in situ. Breast carcinoma in situ is classified into two types:
- DCIS is the condition where abnormal cells are discovered in the lining of a breast duct. The abnormal cells have not spread to other breast tissues outside the duct. DCIS can progress to invasive breast cancer, which can sometimes spread to other tissues. There is not any way to know which lesions will become invasive now.
- Paget disease of the nipple is that condition in which abnormal cells are found in the nipple’s skin cells and can spread to the areola. The TNM system has not staged it. If both Paget disease and invasive breast cancer are present, the TNM system is used to stage the latter.
- T1: The tumour is 20 millimetres or less in size. T1 tumours are classified into four subtypes based on their size:
- T1mi: the tumour is 1 millimetre or less in size.
- T1a: the tumour is larger than 1 millimetre but less than 5 millimetres.
- T1b: the tumour is larger than 5 millimetres but less than 10 millimetres.
- T1c: the tumour is larger than 10 millimetres but less than 20 millimetres.
- T2: The tumour is larger than 20 millimetres but less than 50 millimetres.
- T3: The tumour is larger than 50 millimetres in diameter.
- T4: The cancer is classified as one of the following:
- T4a: the tumour has penetrated the chest wall.
- T4b: the tumour has grown into the skin, forming an ulcer on the surface of the skin on the breast, small tumour nodules in the same breast as the primary tumour, and/or swelling of the skin on the breast.
- T4c: the tumour has invaded the chest wall and skin.
- T4d: inflammatory breast cancer—one-third or more of the breast skin is red and swollen (peau d’orange).
- Node Lymphatic (N). The size and location of lymph nodes affected by cancer.
- Pathologic staging describes lymph nodes after they have been surgically removed and examined under a microscope by a pathologist. The pathologic staging of lymph nodes is explained further below.
- The lymph nodes cannot be evaluated.
- N0: No evidence of cancer in the lymph nodes or tiny clusters of cancer cells in the lymph nodes no larger than 0.2 millimetres in size.
- Cancer is classified as one of the following:
- N1mi: cancer has spread to the axillary (armpit) lymph nodes and is larger than 0.2 millimetres but less than 2 millimetres in size.
- N1a: cancer has spread to 1 to 3 axillary lymph nodes, with at least one lymph node containing cancer larger than 2 millimetres.
- N1b: cancer has spread to lymph nodes near the breastbone on the same side of the body as the primary tumour, the cancer is larger than 0.2 millimetres in size, and the cancer is discovered through sentinel lymph node biopsy. There is no cancer in the axillary lymph nodes.
- N1c: cancer has spread to 1 to 3 axillary lymph nodes and is larger than 2 millimetres in at least one of the lymph nodes. Cancer is also discovered through sentinel lymph node biopsy, performed on lymph nodes near the breastbone on the same body side as the primary tumour.
- Cancer is classified as one of the following:
- N2a: cancer has spread to 4 to 9 axillary lymph nodes, with at least one lymph node containing cancer larger than 2 millimetres.
- N2b: cancer has spread to lymph nodes near the breastbone, and imaging tests reveal the presence of cancer. Cancer in the axillary lymph nodes is not detected by sentinel lymph node biopsy or dissection.
- Cancer is classified as one of the following:
- N3a: cancer has spread to 10 or more axillary lymph nodes, with at least one lymph node containing cancer larger than 2 millimetres, or cancer has spread to lymph nodes below the collarbone.
- N3b: cancer has spread to 1 to 9 axillary lymph nodes, with at least one lymph node containing cancer larger than 2 millimetres. Cancer has also spread to lymph nodes near the breastbone, and imaging tests reveal the presence of cancer; or
- Cancer has spread to 4 to 9 axillary lymph nodes, with cancer in at least one measuring more than 2 millimetres in diameter. Cancer has also spread to lymph nodes near the breastbone on the same side of the body as the primary tumour, and the cancer is larger than 0.2 millimetres in size and was discovered through sentinel lymph node biopsy.
- N3c: cancer has spread to lymph nodes on the same side of the body as the primary tumour.
- Clinical staging refers to the examination of lymph nodes using mammography or ultrasound. The clinical staging of lymph nodes is not covered in this article.
- Metastasis (M) (M). Cancer spreads to other areas of the body.
- M0: There is no evidence that cancer has spread to other parts of the body.
- M1: Cancer has spread to other body parts, most commonly the bones, lungs, liver, or brain. If cancer has spread to distant lymph nodes, cancer in the lymph nodes is larger than 0.2 millimetres. The cancer is known as metastatic breast cancer.
Grading System
The grading system describes the rate at which a breast tumour is likely to grow and spread. The tumour is graded based on how abnormal the cancer cells and tissue appear under a microscope and how quickly the cancer cells are likely to grow and spread. Low-grade cancer cells resemble normal cells and grow and spread slower than high-grade cancer cells.
The pathologist will evaluate the following three features to determine how abnormal the cancer cells and tissue are:
- What proportion of the tumour tissue has normal breast ducts?
- The size and shape of the tumour cells’ nuclei.
- The number of dividing cells present measures how quickly tumour cells grow and divide.
- The pathologist assigns a score of 1 to 3 to each feature; a score of “1” means the cells and tumour tissue look the most normal, and a score of “3” means the cells and tissue look the most abnormal. Each feature’s score is added to yield a total score between 3 and 9.
- There are three possible grades:
- G1 with a total of 3 to 5: (Low grade or well differentiated).
- G2 has a total score of 6 to 7. (Intermediate grade or moderately differentiated).
- G3 with a total score of 8 to 9. (High grade or poorly differentiated).
Biomarker Testing
Biomarker testing is used to determine whether or not breast cancer cells have specific receptors.
Healthy breast cells and some breast cancer cells have receptors (biomarkers) that bind to the oestrogen and progesterone hormones. These hormones are required for the growth and division of healthy cells and some breast cancer cells. To test for these biomarkers, tissue samples containing breast cancer cells are extracted during a biopsy or surgery. In a laboratory, the samples are examined to determine whether the breast cancer cells have oestrogen or progesterone receptors.
HER2 is another type of receptor (biomarker) found on the surface of all breast cancer cells. Breast cancer cells require HER2 receptors to grow and divide.
Biomarker testing for breast cancer includes the following:
- Estrogen receptor type (ER). Breast cancer cells with oestrogen receptors are ER-positive (ER+). Breast cancer cells are called ER-negative if they lack oestrogen receptors (ER-).
- Receptor for progesterone (PR). Breast cancer cells with progesterone receptors are called PR-positive (PR+). Breast cancer cells that lack progesterone receptors are referred to as PR negative (PR-).
- HER2/neu or HER2 is a human epidermal growth factor type 2 receptor. Breast cancer cells are HER2 positive (HER2+) if they have an abnormally high number of HER2 receptors on their surface. Breast cancer cells with a normal amount of HER2 on their surface are called HER2 negative (HER2-). HER2+ breast cancer grows and divides more quickly than HER2- breast cancer.
Breast cancer cells are sometimes described as triple negative or triple positive.
- Three negatives. Breast cancer cells are classified as triple negative if they lack oestrogen receptors, progesterone receptors, or an abnormally high number of HER2 receptors.
- Three cheers. If the breast cancer cells have got oestrogen receptors, progesterone receptors, and an abnormally high number of HER2 receptors, the cancer cells are called triple positive.
The oestrogen receptor, progesterone receptor, and HER2 receptor status must be known to choose the best treatment. Some drugs can prevent cancer from growing by preventing the receptors from attaching to the hormones oestrogen and progesterone. Other drugs may inhibit the growth of breast cancer cells by blocking the HER2 receptors on their surfaces.
Staging Examples
The TNM system, grading system, and biomarker status are used to determine the Stage of breast cancer.
Here are three examples of how the TNM system, grading system, and biomarker status can be used to determine the Pathological Prognostic breast cancer stage for a woman whose first treatment was surgery:
If the tumour is 30 millimetres in diameter (T2), hasn’t spread to nearby lymph nodes (N0), hasn’t spread to distant parts of the body (M0), and is:
Cancer has reached Stage IIA.
If the tumour is 53 millimetres in diameter (T3), has spread to 4–9 axillary lymph nodes (N2), has not spread to other parts of the body (M0), and is:
The tumour has reached Stage IIIA.
If the tumour is 65 millimetres in diameter (T3), has spread to three axillary lymph nodes (N1a), has spread to the lungs (M1), and is:
Cancer has progressed to Stage IV (metastatic breast cancer).
Discuss your breast cancer stage with your doctor and how it is used to plan the best treatment for you.
Following surgery, your doctor will receive a pathology report describing the size and location of the primary tumour; cancer spread to nearby lymph nodes, tumour grade, and specific biomarkers. The pathology report and other test results determine your breast cancer stage.
You’re bound to have a lot of questions. Inquire with your doctor about how staging is used to determine the best treatment options for your cancer and whether there are any clinical trials that might be appropriate for you.
National Cancer Institute provides materials on this page.
