The extent, or stage, of your breast cancer gives your doctor an idea of your prognosis — the likely outcome of your disease — and helps guide treatment decisions.
Your doctor determines your stage of breast cancer through examination of the tissue removed during a mastectomy or lumpectomy and of the lymph nodes under your arm.
Your breast cancer stage takes into account how large your cancer is and whether it has spread beyond your breast. Using this information, your doctor assigns a Roman numeral — I through IV — that describes your breast cancer stage.
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You have stage I breast cancer if all of the following are true:
- The tumor is no more than 2 cm (3/4 inch) in diameter — about the size of a peanut without the shell.
- The cancer hasn’t spread to your lymph nodes.
- The cancer hasn’t spread outside your breast.
A stage II breast tumor is larger than a stage I tumor, but the cancer hasn’t spread to a distant part of your body. If your cancer is stage II, one of the following is true:
- The tumor is 2 to 5 cm (3/4 to 2 inches) in diameter. The cancer may or may not have spread to your underarm (axillary) lymph nodes.
- The tumor is more than 5 cm (2 inches) in diameter — about the size of a lime — but the cancer hasn’t spread to your axillary lymph nodes.
- The tumor is less than 2 cm (3/4 inch) in diameter, but the cancer has spread to no more than three of your axillary lymph nodes.
- No tumor is found in the breast, but breast cancer cells are detected in no more than three of your axillary lymph nodes.
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If you have stage III breast cancer, known as locally or regionally advanced cancer, your cancer may have spread to lymph nodes near your breast — those located under your arm or by your collarbone — but not to more-distant parts of your body.
Here are some examples:
- The tumor is larger than 5 cm (2 inches), with cancer cells that have spread to your axillary lymph nodes. However, the nodes aren’t attached to one another.
- The tumor is smaller than 5 cm (2 inches), but the cancer has spread into nearby lymph nodes and the nodes are growing into each other or the surrounding tissue (stroma).
- The tumor is smaller than 5 cm (2 inches), but the cancer has spread to the lymph nodes above your collarbone.
Inflammatory breast cancer is a form of cancer in which there may be no lump or mass felt in the breast. In inflammatory breast cancer, cancer cells block the lymphatic vessels in breast skin, causing swelling, redness, and ridged or dimpled skin. Inflammatory breast cancer is classified as stage III breast cancer.
Stage IV is the most advanced form of breast cancer.
At this stage, breast cancer cells have spread to other areas of your body. Breast cancer most often spreads to the bones, brain, liver and lungs. Stage IV breast cancer is also called metastatic breast cancer.
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For more information about breast cancer, visit www.mayoclinic.org.