'Lizbeth,
Most comprehensive answer I have ever seen!
Catherine,
Stage is an number assigned depending on how large the tumor is and how far the tumor has spread - how many lymph nodes and which lymph node groups, skin or chest wall involvement and if is has spread to more distant organs (metastases). It is quite complex and a link is given below. Your friend will find out about her stage after testing, imaging and surgery is done, or earlier if neoadjuvant therapy (= chemotherapy before surgery ) is planned.
Both grade and stage as well as hormone and HER2 status are used to estimate prognosis and help decide treatment. Other things such as position of the tumor, number of tumors, and lymphovascular invasion, and Ki67 status ( proliferation marker) may also influence treatment.
http://www.cancer.org/cancer/breastc...cancer-staging
Best wishes to you and your friend
Aussie Girl