Lymph nodes are small, bean-shaped glands that function as filters within the lymphatic system, a major part of the body’s immune defense. They form a drainage network for the entire breast area. This network collects and filters lymph, a clear fluid containing waste products, cellular debris, and foreign invaders. Since the breast is a vascular and glandular organ, it relies heavily on this system to monitor and clear fluid from its tissues.
Where Lymph Nodes Near the Breast Are Located
Lymphatic drainage from the breast flows into several groups of lymph nodes situated across the chest, armpit, and collarbone region. The most significant and well-known group is the axillary lymph nodes, located in the armpit area. Approximately 75% of the lymph fluid from the breast tissue, particularly from the outer quadrants, drains into this axillary basin.
The axillary nodes are further categorized into three levels based on their proximity to the pectoralis minor muscle, with Level I being the farthest and Level III the closest to the chest wall. Some breast tissue, known as the axillary tail, extends into the armpit, making the axillary nodes the primary drainage site for most of the breast. This location is where a person is most likely to feel a swollen node.
A second pathway involves the internal mammary lymph nodes (parasternal nodes), located deep inside the chest. These nodes run alongside the breastbone (sternum) and receive approximately 20% of the lymph fluid, mainly from the breast’s inner quadrants. Because of their deep location behind the ribs, these nodes cannot be felt from the surface.
The third set of nodes includes the supraclavicular nodes, located above the collarbone, and the infraclavicular nodes, found below it. These nodes act as secondary or tertiary drainage points, often receiving lymph that has already passed through the axillary nodes. These three primary groups are interconnected, allowing fluid and cells to travel between them, creating a widespread surveillance system for the entire breast area.
The Role of Lymph Nodes in Breast Health
The function of these lymph nodes is to maintain constant immune surveillance of the breast tissue, acting as checkpoints for the lymph fluid. As lymph fluid flows into the nodes, it passes through specialized compartments filled with immune cells, such as lymphocytes (T-cells and B-cells). These immune cells are responsible for identifying and destroying pathogens like bacteria and viruses, effectively filtering the lymph before returning the fluid to the bloodstream.
This filtration process protects the breast from infection and inflammation. When foreign material is present, it triggers a rapid response, causing immune cells within the node to multiply. The lymphatic system provides defense against local threats by filtering the lymph.
Why Lymph Nodes Swell or Change
When a lymph node becomes enlarged or tender (lymphadenopathy), it signals that the immune system is highly active. The most common reasons for this swelling are benign (non-cancerous). A simple infection, such as a cold, flu, or a skin infection on the arm or hand, can cause the axillary nodes to temporarily swell as they fight invading germs.
Another temporary cause of swelling can be a reaction to a recent vaccination, as the immune system activates its defenses. In these benign cases, the lymph node enlargement is typically temporary, often resolving on its own within a few weeks as the body successfully clears the infection. The node may feel soft, tender, and movable under the skin.
However, lymph node changes are also a concern in the context of disease, most notably breast cancer. If cancer cells break away from a tumor in the breast, they often travel through the lymphatic vessels to the nearest lymph node, which is termed the sentinel lymph node. Finding cancer cells in these sentinel nodes is an important factor in staging the disease and planning treatment.
A node that is hard, fixed in place, and does not seem to shrink after several weeks warrants prompt medical attention, even if no other symptoms are present. While most swollen nodes are due to benign causes, any persistent or unexplained change in the lymph nodes near the breast should be evaluated by a healthcare provider for proper diagnosis.