Intramammary lymph nodes are normal structures found within breast tissue. They are a component of the body’s lymphatic system, playing a role in breast health. This article explores what intramammary lymph nodes are and how often they contain cancerous cells.
What Are Intramammary Lymph Nodes?
Intramammary lymph nodes are small, bean-shaped organs located entirely within the breast’s fatty and glandular tissue, distinct from those in the armpit (axillary) or collarbone areas. They are a natural part of the lymphatic system, a network of vessels and nodes that filter waste and fluid, specifically draining lymphatic fluid from the breast.
These lymph nodes are a common finding during breast imaging, often appearing incidentally during mammograms or ultrasounds. On mammograms, they are frequently seen in about 5% of cases. A normal intramammary lymph node typically measures less than 1 centimeter in diameter and has an oval or kidney-bean shape with a characteristic fatty center, known as a hilum.
How Often Are Intramammary Lymph Nodes Cancerous?
Finding cancer within an intramammary lymph node is considerably less common than encountering benign changes, such as inflammation or reactive enlargement. When malignancy is present, it most frequently represents a spread of cancer from a primary breast tumor within the same breast. In a meta-analysis, the overall incidence of such metastatic involvement was reported to be around 1%.
Cancerous cells found in intramammary lymph nodes are typically from breast carcinoma. These nodes can be an independent indicator of a less favorable outlook for breast cancer patients. While often occurring alongside cancer spread to the axillary lymph nodes, isolated involvement of intramammary nodes can also happen.
Primary lymphoma, a cancer originating in the lymph node itself, is exceedingly rare in intramammary lymph nodes. Instead, benign conditions like reactive hyperplasia, which is an enlargement due to an immune response, or silicone-induced lymphadenopathy, which can occur with breast implants, are far more frequent reasons for changes in these nodes. The majority of intramammary lymph nodes detected during imaging are benign and do not require further investigation.
Evaluation of Intramammary Lymph Nodes
Intramammary lymph nodes are frequently identified during routine breast imaging, including mammography, ultrasound, and magnetic resonance imaging (MRI). Radiologists examine these nodes for specific characteristics that might suggest a potential issue. Normal nodes typically have a distinct oval or kidney-bean shape, a smooth outline, and a visible fatty hilum.
Features that raise suspicion for malignancy include an increase in size, typically greater than 1 centimeter. Changes in shape, such as becoming more rounded or lobulated, are also considered. A diminished or absent fatty hilum, or an increase in the thickness of the outer layer (cortex) of the node, particularly if it’s 3 millimeters or more, can be concerning. Alterations in blood flow patterns within the node, visible on Doppler ultrasound, or an increase in density over time may also prompt further assessment.
If suspicious features are observed, additional imaging studies, such as a breast MRI, may be recommended for a more detailed evaluation. If findings remain concerning, a biopsy is often performed to determine the nature of the node. This procedure involves a fine needle aspiration or core needle biopsy to obtain tissue for microscopic examination. For patients without a known breast cancer diagnosis, a biopsy is generally recommended only when highly suspicious features are present, such as a complete loss of the fatty hilum or a cortical thickness of 5 millimeters or more.
What It Means If Cancer Is Found
When cancer is detected within an intramammary lymph node, it most commonly indicates that cancer cells have spread from a primary breast tumor located within the same breast. This finding directly impacts the staging of the breast cancer. The presence of cancerous cells in these nodes can result in an upstaging of the disease, which influences the overall classification of the cancer’s extent.
This information is important for guiding treatment decisions and planning. The identification of cancer in an intramammary lymph node often leads to adjustments in a patient’s therapeutic approach. The involvement of these nodes is also associated with a less favorable prognosis for breast cancer patients.