Breast cancer is divided into stages 0 through IV.
The term, Stage 0, is used for non-invasive breast cancers like DCIS. In this stage, physicians cannot find any evidence of cancer cells in the normal breast tissue.
Stage I refers to breast cancer that has spread to the surrounding breast tissue. Within this stage, tumors are either less than two centimeters in size and are contained within the breast or are over two centimeters or have spread to the lymph nodes.
Breast cancer in Stage II is typically between two and five centimeters. It may be found in the lymph nodes or axillary lymph nodes.
Stage III breast cancers are larger than five centimeters in diameters. They may be present in up to nine axillary lymph nodes. Inflammatory breast cancer may also develop in Stage III, through it is very rare.
Finally, Stage IV breast cancer has spread outside of the breast tissue and nearby lymph nodes. This stage is used when cancer reaches such organs as the skin, liver, or lungs. It is often referred to as “advanced” or “metastatic” breast cancer.
Staging may also be done using the TNM – or tumor, node, metastasis – system. You can read more about that staging system here.