Axillary lymph nodes are in the armpits, which are close to the breasts. Because the axillary lymph nodes are so close, breast cancer usually spreads to them before other lymph nodes. If cancer has spread to the axillary lymph nodes, a doctor may recommend removing some or all of the lymph nodes during a mastectomy.

If breast cancer is metastatic, it spreads first to the axillary lymph nodes. It can also spread to the lymph nodes in the collar bone or near the breastbone.

Breast tumors most commonly cause drainage toward your axilla or underarm area. Checking this should be part of a clinical breast exam, as well as your monthly self-exam. Although swollen lymph nodes might be evidence that cancer has spread beyond your breast, the only way to know for sure is to have some removed and tested.