Here is a description of the diagnostic stages of breast cancer:
Early stage or stage 0 breast cancer is when the disease is localized to the breast with no evidence of spread to the lymph nodes (carcinoma in situ).
Stage 1 breast cancer: The cancer is two centimeters or less in size and it hasn't spread anywhere.
Stage 2A breast cancer is a tumor less than two centimeters across with lymph node involvement, or a tumor that is larger than two (but less than five) centimeters across without underarm lymph node involvement.
Stage 2B is a tumor that is greater than five centimeters across without lymph node involvement, or a tumor that is larger than two but less than five centimeters across with lymph node involvement.
Locally advanced breast cancer (metastatic) results after cancer cells spread to the lymph nodes.
Stage 3A breast cancer is also called locally advanced breast cancer. The tumor is larger than five centimeters and has spread to the lymph nodes under the arm, or a tumor that is any size with involvement of 4-9 axillary lymph nodes.
Stage 3B breast cancer is a tumor of any size that has spread to the skin, chest wall, or internal mammary lymph nodes (located beneath the breast and inside the chest). Inflammatory breast cancer falls into this category.
Stage 3C breast cancer is a tumor of any size that has spread to more than 10 axillary lymph nodes.
Stage 4 breast cancer is defined as a tumor, regardless of size, that has spread to places far away from the breast, such as bones, lungs, liver, brain, or distant lymph nodes.