The staging of breast cancer refers to the extent of the disease.
The cancer stage is based on several factors, including the size of the tumor, if any lymph nodes are involved,
if the cancer is invasive or non-invasive and if the cancer has spread to areas beyond the breast.
Stage 0 is considered a non-invasive breast cancer. In this stage, there is no evidence that the cancer cells have spread into neighboring breast tissue beyond the duct or lobule.
Stage I is considered an early stage of invasive breast cancer.
When measured, the tumor is no more than 2 centimeters in diameter and there is no evidence that the cancer cells have spread beyond the breast.
Stage II is divided into subcategories of IIA and IIB.
Stage IIA is invasive breast cancer where the tumor is either a maximum of 2 centimeters in diameter and has spread to the lymph nodes under the arm,
or the tumor is between 2 and 5 centimeters in diameter but has not spread to any lymph nodes.
Stage IIB is a little different in that the tumor is either between 2 and 5 centimeters and has spread to under arm lymph nodes,
or the tumor is larger than 5 centimeters but has not spread to the under arm lymph nodes.
Stage III is considered a locally advanced cancer and it is also divided into subcategories of IIIA, IIIB, and IIIC.
There are two main scenarios that can occur with Stage IIIA breast cancer.
One, where the tumor is no larger than 5 centimeters in diameter, but it has spread to under arm lymph nodes that are growing into each other, forming clumps.
The cancer may also have spread to the lymph nodes near the breastbone.
The second scenario for Stage IIIA is very similar with the exception that the tumor is larger than 5 centimeters in diameter and that the underarm lymph nodes are not adhered to one another or other tissues.
Unlike the other stages, in Stage IIIB the tumor may be any size and has spread into the skin of the breast or chest wall.
This stage may also include lumps in the skin of the breast or swelling of the breast.
In Stage IIIC the tumor may also be of any size but it has also spread to lymph node areas above or below the clavicle, the chest wall, and/or the skin of the breast.
Stage IV is considered distant metastatic cancer, meaning the cancer has spread to other organs and parts of the body.