A lymph node is a small, bean-shaped gland that functions as part of the body’s immune system. Lymph nodes near the breast serve as filters for the fluid draining from the breast and surrounding structures. They are connected by lymphatic vessels, which carry a clear fluid called lymph, helping to maintain fluid balance and protect against foreign invaders.
The Role of Lymph Nodes in the Body
The lymphatic system’s primary function is to collect excess fluid, called lymph, that leaks out of blood vessels into the body’s tissues and return it to the bloodstream. This process is necessary for maintaining proper fluid levels and filtering waste products from the body’s cells. Lymph nodes act as centralized collection and processing centers along these vessels. They essentially serve as surveillance stations for the body.
Inside the nodes are specialized white blood cells, including lymphocytes, which constantly monitor the lymph fluid. When the immune system detects foreign particles, such as bacteria, viruses, or abnormal cells, these immune cells rapidly multiply and mount a defense. The nodes trap and destroy harmful substances, preventing them from spreading further into the body.
Location of Lymph Nodes Near the Breast
Lymph nodes associated with the breast are primarily clustered in the armpit, an area known as the axilla. These axillary lymph nodes receive the majority of the lymphatic drainage from the breast. The axillary nodes are typically divided into three levels based on their relationship to the pectoralis minor muscle.
Beyond the armpit, other drainage pathways exist. Some lymph fluid travels to the internal mammary nodes, which are located deep within the chest along the breastbone. Fluid may also drain toward the supraclavicular nodes, found just above the collarbone. This pattern of drainage is important because it indicates the first place that abnormal cells leaving the breast tissue would likely travel.
Why Lymph Nodes Become Swollen or Enlarged
When a lymph node enlarges, a condition called lymphadenopathy, it signals that the immune system is active. The most frequent cause of swelling is a common infection, such as a cold, flu, or a minor injury in the arm or hand. In these benign scenarios, white blood cells rapidly proliferate to fight the infection, causing the node to swell and sometimes become tender.
Swelling can also occur due to inflammatory conditions, including autoimmune disorders or reactions to recent vaccinations. The enlargement is the physical manifestation of the immune response working to neutralize a threat. Generally, nodes swollen from infection are soft, movable, and return to their normal size once the illness resolves. This response is the immune system working as intended.
A more serious reason for enlargement is the presence of cancer cells that have traveled from a nearby tumor, such as breast cancer. When cancer cells break away, they can be filtered out and trapped within the lymph nodes, leading to swelling. Nodes involved with cancer are often described as being hard, fixed in place, and non-tender, providing important clues about the underlying cause.
Lymph Node Assessment in Breast Health Screening
During a standard breast health screening, a clinician performs a physical examination that includes palpation, or gently feeling, the breast and surrounding lymph node areas. The purpose of palpation is to detect any enlarged, firm, or fixed nodes in the armpit or above the collarbone. Palpable nodes may prompt further investigation to determine the cause of the enlargement.
If there is concern, imaging tests are used for a detailed assessment, with ultrasound being the most common method for evaluating axillary nodes. On an ultrasound, a normal lymph node typically appears oval-shaped, measures less than 10 millimeters in diameter, and has a bright central area called the fatty hilum. Abnormal or suspicious nodes often lose their oval shape, become more rounded, and show thickening of the outer layer, or cortex. These visual characteristics help clinicians differentiate between benign and malignant changes.
The definitive method for determining if a suspicious lymph node contains cancer cells is a biopsy, most commonly a fine-needle aspiration. This procedure involves using a thin needle, often guided by ultrasound, to remove a small sample of cells from the node. The collected cells are then examined under a microscope by a pathologist to confirm the presence or absence of disease.