Also known as metastatic breast cancer, the cancer in this stage has spread beyond the breast, underarm and internal mammary lymph nodes to other parts of the body near to or distant from the breast. The cancer has spread elsewhere in the body. The affected areas may include the bones, brain, lungs or liver and more than one part of the body may be involved.
At stage IV, TNM designations help describe the extent of the disease. Higher numbers indicate more extensive disease. Most commonly, stage IV breast cancer is described as:
T: T1, T2, T3 or T4, depending on the size and/or extent of the primary tumor.
N1: Cancer has spread to the lymph nodes
M1: The disease has spread to other sites in the body