Breast cancer is typically staged using the TNM system, which stands for Tumor, Node, and Metastasis. The TNM system helps describe the extent of the cancer based on the size of the tumor, whether it has spread to nearby lymph nodes, and whether it has metastasized (spread to other parts of the body). These elements are combined to determine the stage of breast cancer, which can range from 0 to IV. The four main stages of breast cancer are:
1. Stage 0 (in situ):
This stage is also known as carcinoma in situ. It refers to cancer that is still confined to the ducts (ductal carcinoma in situ, DCIS) or lobules (lobular carcinoma in situ, LCIS) of the breast and has not invaded nearby tissues. It is considered a very early stage of breast cancer.
2. Stage I:
In this stage, the tumor is small (typically less than 2 cm in size) and has not spread to the lymph nodes or distant sites. Stage I breast cancer is divided into two subcategories: Stage IA and Stage IB, depending on the size of the tumor.
3. Stage II:
At this stage, the tumor may be larger (between 2 cm and 5 cm) or may have spread to nearby lymph nodes, but it has not yet metastasized to distant organs. Stage II breast cancer is also divided into subcategories, such as IIA and IIB, based on the size of the tumor and lymph node involvement.
4. Stage III:
This stage is considered locally advanced breast cancer. It may involve a larger tumor (more than 5 cm), extensive lymph node involvement, or invasion of nearby structures, such as the chest wall or skin. Stage III breast cancer is further divided into subcategories, such as IIIA, IIIB, and IIIC, based on the extent of the disease.
5. Stage IV:
This is the most advanced stage of breast cancer, often referred to as metastatic breast cancer. In Stage IV, the cancer has spread to distant organs, such as the lungs, liver, bones, or brain. It is no longer considered curable, but it can be managed with treatments aimed at controlling the disease and improving quality of life.
Breast cancer staging helps guide treatment decisions and prognosis. It’s important to note that these stages can vary in complexity and may involve additional factors, such as hormone receptor status and HER2 status, which further influence treatment options. A healthcare provider will use various tests and imaging studies to determine the stage of breast cancer accurately.