The Stages of Breast Cancer

The stage of breast cancer depends on the size of the breast tumor and whether it has spread to lymph nodes or other parts of the body.
Doctors describe the stages of breast cancer using the Roman numerals 0, I, II, III, and IV and the letters A, B, and C.
A cancer that is Stage I is early-stage breast cancer, and a cancer that is Stage IV is advanced cancer that has spread to other parts of the body, such as the liver.
The stage often is not known until after surgery to remove the tumor in the breast and one or more underarm lymph nodes.
Stage 0
Stage 0 is carcinoma in situ. In ductal carcinoma in situ (DCIS), abnormal cells are in the lining of a breast duct, but the abnormal cells have not invaded nearby breast tissue or spread outside the duct.
Stage IA
The breast tumor is no more than 2 centimeters (no more than 3/4 of an inch) across. Cancer has not spread to the lymph nodes
Stage IB
The tumor is no more than 2 centimeters across. Cancer cells are found in lymph nodes.
Stage IIA
The tumor is no more than 2 centimeters across, and the cancer has spread to underarm lymph nodes.
Or, the tumor is between 2 and 5 centimeters (between 3/4 of an inch and 2 inches) across, but the cancer hasn't spread to underarm lymph nodes.
Stage IIB
The tumor is between 2 and 5 centimeters across, and the cancer has spread to underarm lymph nodes.
Or, the tumor is larger than 5 centimeters across, but the cancer hasn't spread to underarm lymph nodes.
Stage IIIA
The breast tumor is no more than 5 centimeters across, and the cancer has spread to underarm lymph nodes that are attached to each other or nearby tissue. Or, the cancer may have spread to lymph nodes behind the breastbone.
Or, the tumor is more than 5 centimeters across. The cancer has spread to underarm lymph nodes that may be attached to each other or nearby tissue. Or, the cancer may have spread to lymph nodes behind the breastbone but not spread to underarm lymph nodes.
Stage IIIB
The breast tumor can be any size, and it has grown into the chest wall or the skin of the breast. The breast may be swollen or the breast skin may have lumps.
The cancer may have spread to underarm lymph nodes, and these lymph nodes may be attached to each other or nearby tissue. Or, the cancer may have spread to lymph nodes behind the breastbone.
Stage IIIC
The breast cancer can be any size, and it has spread to lymph nodes behind the breastbone and under the arm. Or, the cancer has spread to lymph nodes above or below the collarbone.
Stage IV
The tumor can be any size, and cancer cells have spread to other parts of the body, such as the lungs, liver, bones, or brain.