Breast cancer can be defined as malignant or cancerous cells in the breast. The cells can also spread to the lymph nodes, part of the immune system in the body, and to the lung, liver, bone and brain, in which case it is referred to as metastatic breast cancer.
Breast cancer is commonly ‘staged’ from 0 to IV by doctors, who give the cancer a TNM score, which stands for Tumor, Node, Metastasis. A small tumor, no node involvement and no spread would be Stage 0, while a large tumor and node involvement might be a Stage III. Any metastasis or spread is a Stage IV.
Staging is important because it helps doctors decide the best treatments in each case. The National Comprehensive Cancer Network is a group of leading cancer care centers throughout the US which set guidelines to help doctors in all practices follow similar procedures that have been tried and tested in order to get the best outcome (prognosis) possible. Here are some inspiration quotes.