Mammary lymph nodes are small, bean-shaped organs that form a part of the body’s extensive lymphatic system. This system is a network of vessels, tissues, and organs working to defend the body against infection and disease. Lymph nodes act as filters for lymph fluid, a clear fluid that circulates throughout the body. They contain specialized white blood cells, called lymphocytes, which play a direct role in fighting off foreign invaders like bacteria and viruses.
Location and Normal Function
Mammary lymph nodes are found in various locations surrounding the breast tissue. Approximately 75% of lymphatic drainage from the breast flows into the axillary lymph nodes, located in the armpit. Other groups include the parasternal lymph nodes, also known as internal mammary nodes, situated along the breastbone, and the supraclavicular nodes, located above the collarbone.
These lymph nodes function as filters, trapping harmful substances that travel through the lymphatic fluid, including pathogens like bacteria and viruses, and abnormal cells. They house immune cells that are activated when foreign substances are detected. This activation initiates an immune response to eliminate the threat. Their proper functioning is essential for maintaining overall health.
Mammary Lymph Nodes and Breast Cancer
The lymphatic system provides a pathway for breast cancer cells to spread from the primary tumor. Cancer cells can detach from the breast tumor and enter the lymphatic vessels, traveling to regional lymph nodes, most commonly the axillary nodes. The presence of cancer cells in these lymph nodes indicates that the disease has begun to spread beyond the breast.
Lymph node involvement affects the staging and prognosis of breast cancer. The number of affected nodes directly correlates with the cancer’s stage and influences recurrence likelihood. The TNM staging system considers this involvement. More extensive involvement indicates a less favorable prognosis.
To assess lymph node involvement, specific procedures are performed. A sentinel lymph node biopsy (SLNB) is a common surgical procedure used to identify and remove the “sentinel node” or nodes. These are the first lymph nodes to receive drainage from the breast tumor, making them the most likely initial site for cancer spread. A tracer, often a blue dye or a radioactive substance, is injected into the breast to locate these specific nodes during surgery.
If sentinel nodes are free of cancer cells, it suggests the cancer has likely not spread further, often avoiding more extensive surgery. However, if cancer cells are detected, an axillary lymph node dissection (ALND) may be performed. This procedure involves surgically removing a larger number of lymph nodes from the armpit to determine the full extent of cancer spread. ALND helps oncologists determine how many lymph nodes are affected and guides decisions regarding additional treatments.
Other Conditions and Evaluation
Beyond cancer, mammary lymph nodes can be affected by other conditions, such as infection or inflammation, leading to a condition called lymphadenitis. Benign growths can also occur within these nodes. In such cases, the lymph nodes might become enlarged or tender.
Doctors evaluate mammary lymph nodes through a combination of methods. A physical examination involves palpating, or feeling, the areas where lymph nodes are located to check for any abnormal swelling or tenderness. Imaging techniques like ultrasound or MRI are also used to visualize the lymph nodes and assess their size, shape, and internal characteristics. If a node appears suspicious on imaging or physical exam, a biopsy may be performed to confirm a diagnosis.