Breast cancer can spread by growing into nearby tissues in the breast or when the cancer cells get into and travel through the blood or lymph systems. When this happens, cancer cells may be found in the lymph nodes in the armpit. These lymph nodes are called axillary lymph nodes. They are often checked for cancer as part of the diagnosis process. If the cancer reaches these nodes, it may have spread to other parts of the body.
Breast cancer that has spread to other organs of the body is called metastatic breast cancer. When breast cancer spreads to other parts of the body, it most often goes to the brain, bones, liver, or lungs.
The most important factor in evaluating breast cancer is determining which of these it is:
Noninvasive (in situ) cancer. This occurs only in the ducts and doesn’t spread to nearby areas. If not treated, it can later grow into a more serious, invasive type of cancer. If you are diagnosed with noninvasive ductal carcinoma, your chances of surviving are very high if you don’t wait to treat it. If you do wait, you’re at risk of the cancer becoming invasive. Invasive cancer is harder to treat.
Invasive (infiltrating) cancer. This kind of cancer has started to spread to nearby areas. This type is much more serious than noninvasive cancer. It often invades nearby lymph nodes first. It can then spread to other parts of your body through your bloodstream and lymphatic system. Treatment for invasive cancer is often a more difficult, long-term process.