In 2006, 213,000 new cases of breast cancer were diagnosed, according to The Merck Manuals, an online medical library. This website also reports that breast cancer is the second leading cause of cancer death in women. Doctors use information from a clinical exam, as well as the results of a biopsy or surgery, to assign a stage to breast cancer, which describes how extensively the cancer has grown. Knowing the cancer stage enables the doctor to assess the extent of the disease and make recommendations for methods of treatment.
Stage 0
When breast cancer is at its earliest stage of growth, it is said to be at Stage 0. The American Cancer Society describes Stage 0 breast cancer as "in situ," meaning it has not yet spread throughout the breast tissue or to other sites within the body. The cancer may be in the breast ducts or the breast lobules, which are different types of breast tissue, but has not grown beyond the ducts or lobules, respectively. Individuals with Stage 0 breast cancer may feel no breast lump if the tumor is found early.
Stage I
Stage I breast cancer, according to the American Cancer Society, involves a cancerous lump, also referred to as a cancerous tumor, that is 2 centimeters or less in size; along with this, the cancer has not spread or a very small amount of cancer has been detected, less than 2 millimeters, in one to three of the lymph nodes in the armpit.
Stage II
The Georgetown Lombardi Comprehensive Cancer Center describes the factors that are indicative of Stage II breast cancer. This stage of breast cancer involves a tumor that is up to 5 centimeters in size, with the possibility of a tumor larger than 2 millimeters detectable in the armpit lymph nodes. Cancer may also be found in the mammary lymph nodes. There is a wide range of variability within Stage II breast cancer, and Stage II is usually broken up into two separate stages: Stage IIA and IIB. Generally, if the primary breast tumor is small or undetectable, the cancer will be diagnosed as Stage II rather than Stage I if a substantial amount of cancer has been detected in the armpit or mammary lymph nodes. If the tumor in the breast is larger in size, up to 5 centimeters, but no cancer has been detected in the lymph nodes, the cancer would likely still be diagnosed as Stage II because the tumor is a significant size.
Stage III
In Stage III breast cancer, the Georgetown Lombardi Comprehensive Cancer Center describes that the breast lump may be of any size. The distinguishing factor for Stage III breast cancer is that it has spread to the skin of the breast and/or to the chest wall. It also may have spread to the lymph nodes in the armpit, near the breastbone and/or near the collarbone. Stage III is also usually broken up into distinct stages: Stage IIIA, IIIB and IIIC.
Stage IV
The American Cancer Society states that Stage IV breast cancer is the most advanced stage of breast cancer growth and is indicative of cancer cells that have metastasized, meaning the cancer has spread to distant sites within the body. The primary breast lump in Stage IV, like Stage III, may be of any size. Common sites to which the cancerous cells may have spread include the lung, liver, brain, bones and lymph nodes that are located far away from the breast.
