One of the first priorities after diagnosis of breast cancer is finding out if the cancer has spread to other parts of your body. There are two ways that breast cancer commonly spreads - through the bloodstream and through the lymph node system. Breast cancer spread most commonly occurs through the lymph nodes in the underarm on the same side of the body as the breast tumor. Your healthcare team can test for the spread of cancer to these lymph nodes in several ways. Your surgeon can describe the surgical options to you.