Breast cancer can spread through the blood or through the lymphatic system and may cause nearby lymph nodes to become swollen. Swollen lymph nodes may feel like a lump or area of swelling in the armpit, or lumps or swelling above or below the collarbone.1 However, swollen lymph nodes can also be a sign of other conditions.
What is the lymphatic system?
The lymphatic system is part of the immune system that carries fluid called lymph through the body. The lymphatic system is made up of lymphatic vessels, lymph nodes, collecting ducts, and several organs, including the spleen, thymus, and tonsils. The main functions of the lymphatic system are to eliminate damaged cells from the body and to defend the body against potential infection and cancer.2,3
What are the lymph nodes?
Lymph nodes are bean-shaped structures that are found along the lymphatic vessel pathways. The function of the lymph nodes is to filter the lymph before it goes back to the bloodstream. While lymph nodes are found throughout the body, there are some areas where a cluster of lymph nodes are found, such as the axillary lymph nodes in the armpits, as well as the supraclavicular and infraclavicular lymph nodes above and below the collarbone, respectively. Lymph nodes contain many white blood cells, particularly lymphocytes and macrophages, which are key components of the immune system and help the body fight off infection and remove damaged cells, like cancer cells.2,3
Normally, the lymph nodes cannot be felt. However, lymph nodes can become swollen and are then palpable (able to be felt). Lymph nodes can become swollen due to the presence of a large number of infectious organisms or cancerous cells. Sometimes, people may call swollen lymph nodes “swollen glands,” particularly in reference to the lymph nodes in the neck, however, lymph nodes are not glands.4
How breast cancer spreads
A recent study evaluated the patterns of how breast cancer spreads. Researchers began with the knowledge that the presence of breast cancer in the axillary lymph nodes are a risk factor for breast cancer to metastasize to other organs, but they didn’t know if the presence of the cancer in the axillary lymph nodes were responsible for the cancer spreading or what routes cancer cells take.5,6
By looking at the DNA of the cancer cells and using a technique called next-generation sequencing, researchers were able to analyze the breast cancer cells from the initial tumor, the axillary lymph nodes, as well as other organs. Metastases often spread from the first distant organ to other organs. One of the most important findings was that the cancer cells in the axillary lymph nodes did not necessarily spread directly to other organs. Even if the presence of cancer in these lymph nodes was an indicator of the aggressiveness of the cancer, they were not necessarily the cause of further metastases. Rather, in certain instances, the tumor in the breast developed multiple distant metastases simultaneously.5,6
While this study was small (involving 99 samples from 20 patients with breast cancer), its findings are helping to uncover how breast cancer spreads and can help provide additional information for effective treatments.6
Other symptoms of breast cancer
Besides swollen lymph nodes, breast cancers may cause other symptoms, such as7:
Discharge from the nipple (other than breast milk), possibly bloody fluid
Changes to the areola (the darker area of skin around the nipple), including scaly, red, or swollen tissue
Multiple dimples on the skin of the breast that resembles an orange skin (peau d’orange)
Symptoms of advanced breast cancer. Cancer Research UK. Available at https://www.cancerresearchuk.org/about-cancer/breast-cancer/advanced/symptoms. Accessed 8/2/18.
National Cancer Institute. Available at https://training.seer.cancer.gov/anatomy/lymphatic/components/. Accessed 8/2/18.
Merck Manuals. Available at http://www.merckmanuals.com/home/heart-and-blood-vessel-disorders/lymphatic-disorders/overview-of-the-lymphatic-system. Accessed 8/2/18.
MedlinePlus, U.S. National Library of Medicine. Available at https://medlineplus.gov/ency/article/002247.htm. Accessed 8/2/18.
Breast cancer’s spread routes mapped. Science Daily. Available at https://www.sciencedaily.com/releases/2018/02/180227094640.htm. Accessed 7/17/18.
Ikram Ullah, Govindasamy-Muralidharan Karthik, Amjad Alkodsi, Una Kjällquist, Gustav Stålhammar, John Lövrot, Nelson-Fuentes Martinez, Jens Lagergren, Sampsa Hautaniemi, Johan Hartman, Jonas Bergh. Evolutionary history of metastatic breast cancer reveals minimal seeding from axillary lymph nodes. Journal of Clinical Investigation, 2018; DOI: 10.1172/JCI96149
Breast cancer treatment (PDQ). National Cancer Institute. Available at https://www.cancer.gov/types/breast/patient/breast-treatment-pdq. Accessed 7/30/18.