Lymph nodes are small, bean-shaped glands that are part of the body’s immune system. These structures are connected by a network of lymphatic vessels that transport lymph fluid throughout the body. Their primary role involves filtering this fluid, trapping harmful substances like bacteria, viruses, and abnormal cells, including cancer cells. This filtration process is a fundamental aspect of the body’s defense mechanisms, and understanding lymph nodes is particularly relevant in the context of breast health.
Key Locations of Breast Lymph Nodes
The breast contains a network of lymphatic vessels that drain into several key groups of lymph nodes. The most significant are the axillary lymph nodes, located in the armpit. These nodes receive the majority of lymphatic drainage from the breast, typically 75% to 90% of the lymph fluid.
Axillary lymph nodes are categorized into three levels based on their relationship to the pectoralis minor muscle. Level I nodes are lateral to the muscle, Level II nodes lie beneath or posterior to it, and Level III nodes are medial and superior, extending up to the collarbone.
Internal mammary lymph nodes, also known as parasternal nodes, are found along the breastbone (sternum). These nodes drain lymph from the inner breast, accounting for approximately 10% to 25% of the breast’s lymphatic flow.
Other regional nodes include the supraclavicular lymph nodes, located above the collarbone, and the infraclavicular lymph nodes, found below the collarbone. These additional groups can also receive lymphatic fluid from the breast. The infraclavicular nodes are part of the drainage for the superior breast and upper limb.
Role in Breast Health Assessment
Lymph nodes are important for assessing breast health because changes in their size or texture can signal underlying conditions. Swollen or tender nodes often indicate active filtering of abnormal substances. This response can occur due to infections or inflammation, as immune cells within the nodes combat foreign invaders.
Healthcare providers assess these nodes during a physical examination by feeling areas like the armpit and above the collarbone. This palpation helps determine if the nodes are enlarged, firm, or fixed, which can be signs of concern. Imaging techniques, including ultrasound, mammography, and MRI, also visualize lymph nodes and detect changes not felt during an exam.
The assessment of breast lymph nodes is relevant in the context of cancer. If cancer cells break away from a breast tumor, they often travel through the lymphatic system and can become trapped in nearby lymph nodes. The status of these nodes provides information about the potential spread of cancer and helps guide treatment decisions.
Lymph Node Biopsy Procedures
When lymph node involvement is a concern, particularly in breast cancer, specific procedures obtain tissue samples for examination. The sentinel lymph node biopsy (SLNB) is a common procedure to determine if cancer cells have spread from the primary breast tumor. A sentinel lymph node is the first node or nodes to which cancer cells are most likely to spread.
During an SLNB, a surgeon injects a dye or radioactive tracer near the tumor. This substance travels through lymphatic vessels to highlight the sentinel node(s), typically one to five nodes. The surgeon removes these identified nodes, which are sent to a laboratory for microscopic examination to check for cancer cells. If the sentinel nodes are free of cancer, it suggests the cancer has likely not spread to other lymph nodes, potentially avoiding more extensive surgery.
If cancer is found in sentinel nodes, or if SLNB is not feasible, an axillary lymph node dissection (ALND) may be performed. This procedure involves removing a larger number of lymph nodes from the armpit. ALND is a more extensive surgery, reserved for confirmed lymph node involvement or other specific indications, to assess cancer spread.