After a breast cancer diagnosis, oncologists and breast surgeons stage the cancer. Breast cancer staging describes the extent of cancer in the body. Accurate staging involves multiple factors. Doctors look at the size of the tumor, whether cancer cells have spread the lymph nodes under the arm, and whether cancer cells have spread to other parts of the body. The breast cancer stage at diagnosis determines prognosis and guides treatment. Generally, lower stages have better prognoses and survival rates than higher stages. In fact, the 5-year survival is 98% at the earliest stage, when cancer is small and confined to the breast. What are the stages of breast cancer? Although there are five total stages of breast cancer, doctors use Roman numerals and mark them 0 through IV. Stages 0, I, and some forms of stage II breast cancer are considered early stage breast cancer and stages III and IV are advanced. There is also recurrent breast cancer. Stage 0 Breast Cancer Stage 0 is ductal carcinoma in situ (DCIS). DCIS is the earliest form of breast cancer and is noninvasive: cancer cells are growing inside the milk ducts, but remain in place (in situ). Stage 0 treatment usually involves surgery because the cancer is confined to the breast. Breast-conserving surgery (lumpectomy) or mastectomy are options. In some cases, doctors recommend adding hormone therapy or radiation. Stage I Breast Cancer Stage I includes early forms of invasive breast cancer. The cancer has invaded other breast tissue, but tumors are small, measuring less than 2 cm—less than an inch in diameter. There are two subcategories, IA and IB. Stage IA: Tumor is confined to the breast Cancer cells have not spread. There is no lymph node involvement and no metastasis to other sites in the body. Stage IB: Small groups of breast cancer cells are present in local lymph nodes. Local lymph nodes are those closest to the breast, usually in the underarm area. Stage I treatment typically starts with local therapy—surgery and radiation. A lumpectomy or mastectomy are usually options. Doctors typically recommend adjuvant therapy, which is treatment after surgery to kill any surviving cancer cells. This can include chemotherapy, hormone therapy, or immune-targeted therapy. Stage II Breast Cancer Stage II also includes early forms of invasive breast cancer. The tumor is either larger than Stage I or the cancer has spread to local lymph nodes. There are two subcategories, IIA and IIB: Stage IIA breast cancer includes one of following: No tumor in the breast, but cancer is in one to three local lymph nodes Tumor measures 2 cm or less with cancer in local lymph nodes Tumor measures 2-5 cm with no cancer in the lymph nodes Stage IIB breast cancer includes one of the following: Tumor measures 2-5 cm with cancer in one to three local lymph nodes Tumor is larger than 5 cm with no cancer in the lymph nodes Stage II treatment is similar to Stage I. It starts with local therapy, and then adjuvant therapy afterwards. For women with larger tumors, neoadjuvant therapy is sometimes an option. Neoadjuvant therapy is treatment before surgery to shrink the tumor size. This may allow for breast-conserving surgery instead of a mastectomy. Stage III Breast Cancer Stage III is locally advanced breast cancer. The cancer has spread to nearby lymph nodes and tissues, but has not spread to distant body sites. There are three subcategories, IIIA, IIIB and IIIC: Stage IIIA breast cancer includes one of the following: Any size tumor or no tumor in the breast, with cancer in 4 to 9 local lymph nodes Tumor larger than 5 cm with cancer in one to three local lymph nodes Stage IIIB breast cancer includes one of the following: Tumor has grown into the chest wall with up to 9 lymph nodes affected Tumor has grown out to the skin with up to 9 lymph nodes affected Stage IIIC breast cancer includes one of the following: No tumor in the breast, but cancer has spread to more than 10 local lymph nodes or to more distant lymph nodes Any size tumor in the breast that has also spread to more than 10 local lymph nodes or to more distant lymph nodes Any size tumor in the breast that is invading the chest wall or skin and is also in 10 or more local lymph nodes or other lymph nodes farther away from the breast, such as above or below the collar bone Stage III treatment usually begins with neoadjuvant chemotherapy, hormone therapy, or immune-targeted therapy. The goal is to shrink tumors and allow the surgeon to remove as much cancer as possible. Mastectomy is most common in Stage III. Adjuvant radiation, chemotherapy, hormone therapy, or immune-targeted therapy follows surgery. Stage IV Breast Cancer Stage IV is metastatic breast cancer. Cancer has spread beyond the breast and nearby lymph nodes to organs or other sites in the body. Sites commonly include the bones, lungs, brain, liver, and distant lymph nodes. The tumor can be any size and involve any number of lymph nodes. Treatment can’t cure advanced breast cancer. Instead, treatment can shrink tumors, ease symptoms, and lengthen life. As a result, surgery is not useful in most cases. People with advanced breast cancer need to consider treatment side effects that affect the quality of life. Some people choose to enroll in a clinical trial at this stage to aid in research. Recurrent Breast Cancer Recurrent breast cancer is cancer that returns after treatment. It can occur locally in the same breast, or at a distant site. Cancer in the other breast is a new cancer that needs its own treatment plan. For a local recurrence, treatment will depend on previous treatments. Cancer that occurs at a distant site is treated as Stage IV breast cancer. Key Takeaways Breast cancer’s stage at diagnosis plays a big role in treatment choices and prognosis. The earlier the stage, the better the prognosis. That’s why it’s so important to follow screening recommendations. Women 40 and older at increased risk for developing breast cancer should have an annual screening mammogram and an annual clinical breast exam from their doctor. And all women should be aware of what is normal for their breasts and discuss current breast cancer screening guidelines with their health care provider.