Ductal carcinoma in situ (DCIS) is a noninvasive form of breast cancer. Carcinoma in situ is found on mammography. It is generally not palpable and not characterized by a lump in the breast. The treatment for ductal carcinoma in situ generally involves lumpectomy followed by radiation. Patients can also undergo a simple mastectomy which does not require additional radiation treatment. Women are generally placed on tamoxifen to prevent recurrence of DCIS or development of invasive breast cancer. Traditional chemotherapy is not advocated for patients with DCIS.

Lobular carcinoma in situ (LCIS) is not considered a cancer. It is a risk factor for developing invasive breast cancer. Patients with LCIS have an 21% chance of developing breast cancer over 15 years. LCIS is often multicentric and bilateral. Sometimes LCIS is treated with bilateral prophylactic mastectomy. Often patients with LCIS are placed on tamoxifen, witch has been shown to decrease the risk of invasive breast cancer by approximately 56% (NSABP-P1 trial). Traditional chemotherapy is generally not advocated for patients with LCIS.

The treatment for invasive breast cancer can be difficult to generalize to all people. These issues should be discussed with an oncologist and a surgeon. Patients are often treated with lumpectomy, with axillary lymph node dissection or sentinel lymph node biopsy. Some patients will elect to undergo mastectomy with axillary lymph node dissection or sentinel lymph node biopsy. Often, patients will then receive adjuvant chemotherapy. Two standard regimens, given for adjuvant chemotherapy for invasive breast cancer include Adriamycin and Cyclophosphamide with or without Taxol (AC +/- T) or Cyclophosphamide plus Methotrexate plus Fluorouracil (CMF). Each of these chemotherapy combinations has different potential side effects.

Patients with stage III breast cancer who wish to have Breast-conserving therapy will often choose to undergo neoadjuvant chemotherapy. This means that the chemotherapy is given prior to surgery. Normally chemotherapy is given after surgery, but in the setting of a large breast cancer, giving chemotherapy prior to surgery can sometimes allow for Breast-conserving therapy to be performed. After the surgery the patients will then go on to receive radiation.

Patients with metastatic breast cancer are considered stage IV. Patients can often be treated with hormones, such as tamoxifen anastrazole or fulvstrant. Sometimes these cancers will not be responsive to hormones, and systemic chemotherapy must be used. There is a long list of chemotherapies which can be effective in this setting. Although metastatic breast cancer is generally not considered curable, women can live for extended periods of time with treatment.