The 4 stages of breast cancer
In the staging systems, seven key pieces of information are used include TNM, ER, PR, HER2, and Grade of cancer.
The four stages of breast cancer include
- Stage I: It is divided into two groups.
- Stage IA: Cancer is 2 cm or smaller and has not spread outside the breast.
- Stage IB: Cancer has spread to the lymph node and is between 0.2 and 2 mm in size.
- Stage II: It is divided into two groups.
- Stage IIA: The tumor in the breast is still small. There may or may not be cancer spread to the lymph nodes.
- Stage IIB: Tumor could be the size of a walnut or lime. It may or may not spread to the lymph nodes.
- Stage III: Cancer hasn’t spread to bones or organs. However, it is considered an advanced stage. There are three groups.
- Stage IIIA: The tumor has been found in up to nine lymph nodes in the underarm to the collarbone.
- Stage IIIB: The tumor has grown into the chest wall or skin around the breast.
- Stage IIIC: The tumor has been found in 10 or more lymph nodes or has spread above or below the collarbone.
- Stage IV: Breast cancer cells have spread far away from the breast and lymph nodes around it.
There is one more stage called stage 0 or carcinoma in situ. It means the initial stage where the cancerous cells are confined to their origin and have not acquired the “invasive” character yet.
The staging system most often used for breast cancer is the TNM system of the American Joint Committee on Cancer (AJCC). In this, breast cancer staging may be of two types.
- Clinical staging: Based on the results of tests done before surgery, which may include physical examinations, mammograms, ultrasound, and magnetic resonance imaging (MRI) scans.
- Pathological staging: Based on what is found during surgery to remove breast tissue and lymph nodes.
In both the staging systems, seven key pieces of information are used.
- T (tumor): It refers to the size of the original tumor.
- N (node): It describes whether cancer has spread to the lymph nodes.
- M (metastasis): It refers to the spreading of cancer to other parts of the body.
- Estrogen receptor (ER) status: It refers to the presence of a protein called estrogen receptor in cancer.
- Progesterone receptor (PR) status: It defines whether cancer has a protein called a progesterone receptor.
- HER2 status: It assesses if cancer is producing too much of a protein called HER2 (human epidermal growth factor receptor 2).
- Grade of cancer (G): It refers to how close cancer cells appear like normal cells.
A number (0-4) or the letter X is allocated to each factor. A higher number means the cancer is more advanced. For instance, a T1 score refers to a smaller tumor than a T2 score. The letter X indicates that the information could not be assessed.
Table. The characteristics of breast cancer according to the TNM staging system
| Stages | T Category | N Category | M Category |
|---|---|---|---|
| X | The primary tumor cannot be assessed. | The lymph nodes cannot be assessed. | Distant spread cannot be evaluated. |
| 0 | No evidence of cancer in the breast. | There are two possibilities:
| No distant spread |
| 0is | Cancer is confined within the ducts of the breast tissue and has not spread into the nearby tissue. There are two types:
| – | – |
| 0 (i+) | – | – | No clinical or radiological evidence of metastases. Although there is microscopic evidence of cancer cells in the blood, bone marrow, or other lymph nodes that are no larger than 0.2 mm. |
| I | The tumor in the breast is 20 mm or smaller in size at its widest area. There are four substages:
| Cancer has spread to one or three lymph nodes in the armpit.
| Evidence of metastasis to another part of the body, which means breast cancer cells are growing in other organs. |
| II | The tumor is between 20 and 50 mm. | Cancer has spread to four to nine lymph nodes. | – |
| III | The tumor is larger than 50 mm. | Cancer has spread to 10 or more lymph nodes. | – |
| IV | The tumor falls into one of the following groups: T4a means the tumor has grown into the chest wall. T4b is when the tumor has grown into the skin. T4c is cancer that has grown into the chest wall and the skin. T4d is inflammatory breast cancer. | – | – |
Medically Reviewed on 4/30/2021
References
American Cancer Society. Breast Cancer Stages. https://www.cancer.org/cancer/breast-cancer/understanding-a-breast-cancer-diagnosis/stages-of-breast-cancer.html
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