After breast cancer is diagnosed, staging of the cancer then takes place. Staging is done with surgery and various tests such as PET scans or an MRI to find out if and where the cancer has spread. The stages are a standardized way of describing the pattern of cancer progression and helps to guide treatment and prognosis. In breast cancer, Stages III and IV are the advanced stages of breast cancer, with several substages described as well.
Stage IIIA
The first substage of Stage III breast cancer is Stage IIIA and consists of cancer that is either: less than 5 cm and has spread to four to nine lymph nodes under the armpit or the lymph nodes in the breast are enlarged; or the tumor is bigger than 5 cm but has not spread into the skin of the breast or the chest wall, and has also spread to one to nine lymph nodes under the armpit or has spread to the lymph nodes in the breast. There is no breast cancer in any distant organs in the body in any Stage III breast cancer.
Stage IIIB
According to the American Cancer Society, Stage IIIB breast cancer is diagnosed when the cancer has spread to the chest wall or skin of the breast and also either it has not spread to any lymph nodes; cancer is found in one to three lymph nodes under the arm or microscopic amounts are found in mammary lymph nodes; or four to nine underarm lymph nodes are cancerous or the mammary lymph nodes are enlarged. The National Cancer Institute notes that if a diagnosis of inflammatory breast cancer is made, it is automatically Stage IIIB breast cancer.
Stage IIIC
In the last substage of Stage III breast cancer, the breast tumor is any size or is not found, and also has one of the following characteristics: 10 or more underarm lymph nodes are also cancerous; lymph nodes under or above the collarbone have cancer in them; underarm lymph nodes are cancerous and enlarged lymph nodes in the breast are present; or four or more underarm lymph nodes are cancerous as well as breast lymph nodes.
Stage IV
Stage IV is the most advanced stage of breast cancer and is also known as metastatic breast cancer. This means that the cancer has spread to other organs in the body. Typical places to which breast cancer spreads include the brain, bones, liver and lungs.
