Breast cancer spreads when cancer cells enter the blood or lymph system and travel to other parts of the body. The lymph system, part of your immune system, includes lymph nodes (small glands), vessels, and organs that carry lymph fluid. Breast cancer cells can spread to:
- Lymph nodes under the arm (axillary lymph nodes)
- Lymph nodes near the breastbone (internal mammary lymph nodes)
- Lymph nodes around the collarbone (supraclavicular and infraclavicular lymph nodes)
- If cancer cells are in the lymph nodes, there’s a higher chance they might spread to other parts of the body, but not all women with cancerous lymph nodes will develop metastases.