Breast cancer is the most common cancer among women, but it is not a terminal disease and early detection and treatment is very important. The 10-year survival rate of stage zero breast cancer is nearly 100%, and the 10-year survival rate of both stage I and stage II breast cancer can often reach 80%. In this article, we will look at the definition of stage II breast cancer and how to treat it. Stage II breast cancer is divided into IIA and IIB, and two things must be evaluated: the size of the breast tumor and whether there is metastasis in the axillary lymph nodes. In stage II breast cancer, if the breast tumor is larger than two centimeters, there must be “no metastasis” in the axillary lymph nodes to qualify. If the breast tumor is less than five centimeters and the number of axillary lymph node metastases is 1-3, then it is also a stage II breast cancer. In every discussion of breast cancer treatment, the physician will take into account the patient’s age, physical strength, tumor size, number of lymph node invasions, ER, PR, and HER2 before evaluating the appropriate treatment plan. However, the size of the tumor to be treated with breast-conserving surgery should not be too large (usually no larger than 2 or 3 centimeters). If total mastectomy is not desired, but the tumor is large, “preoperative adjuvant therapy” can be considered to reduce the size of the tumor so that breast conservation surgery can be performed at the next stage. Surgery is a very important treatment for second stage breast. It is considered from two directions. Depending on the physician’s recommendation, the patient’s wishes, and the tumor status, the decision to perform a total mastectomy or breast conservation surgery can be made. If axillary lymph node metastasis is clinically suspected, lymph node dissection is usually performed. If there is no clinical suspicion of axillary lymph node metastasis, anterior lymph node testing may be performed first. The concept of anterior lymph node is that “lymph node drainage is gradual”. Therefore, the physician can first find the “first few lymph nodes” of the patient’s lymphatic drainage by using stains or isotopes, and then take these lymph nodes for testing to see if there is any evidence of cancer metastasis in these lymph nodes. If there is no cancer metastasis in the nearest lymph nodes to the tumor, then we assume that the remaining lymph nodes are healthy and do not need to be removed surgically. If the anterior lymph nodes are determined to have cancer metastasis, then further axillary lymph node contouring surgery should be done. After the surgery, the physician will determine the next treatment plan. For patients who have undergone breast conservation surgery, additional radiation therapy will be required. If the breast tumor is large, radiation therapy may also be considered. Patients with stage II breast cancer usually need chemotherapy to reduce the recurrence rate. Chemotherapy attacks all the fast-growing cells and there are many different combinations of drugs available to treat breast cancer. If the test results show that the cancer cells have ER and PR on the surface, then hormone therapy is indicated to block the stimulation of the cancer cells by hormones. Patients with HER2-positive cancer cells can be treated with targeted therapy, which targets specific targets with little impact on normal cells. Today, patients with early-stage breast cancer are often well treated and even have a chance of recovery. The five- and 10-year survival rates for stage II breast cancer are high. If the concern is total mastectomy, stage II patients may also consider receiving preoperative adjuvant therapy to increase their chances of preserving their breasts, and should never delay their chance to save their lives because of an internal fear of surgery.