A mammogram is an X-ray image used to examine breast tissue, helping detect early signs of breast cancer or other changes. As a routine part of breast health screening, it’s common for lymph nodes to be visible during this process.
Understanding Lymph Nodes
Lymph nodes are small, bean-shaped structures that play a significant role in the body’s immune system. They function as filters for lymph, a clear, watery fluid that circulates throughout the body. As lymph fluid passes through these nodes, immune cells within them work to identify and remove foreign substances, such as bacteria, viruses, and abnormal cells.
Hundreds of lymph nodes are distributed throughout the body, connected by a network of lymphatic vessels. Those particularly relevant to breast health are located in the armpit, known as axillary lymph nodes. There are typically 15 to 30 lymph nodes in the armpit, which drain lymph fluid from the breast and surrounding areas. Lymph nodes can also be found within the breast tissue itself, called intramammary lymph nodes.
Lymph Nodes on a Mammogram: Normal Findings
It is common to see lymph nodes on a mammogram, especially those in the armpit (axilla). These nodes are often captured because mammography views include the breast tissue that extends into the armpit area. Their visibility does not indicate a problem.
Normal-appearing lymph nodes on a mammogram typically have specific characteristics. They are usually small, oval or kidney-shaped, and possess a central fatty area known as a hilum, which appears as a lucent (less dense) notch. These benign lymph nodes are well-defined and generally measure less than 2 centimeters in diameter. Their appearance reflects their healthy function as part of the lymphatic system.
When Lymph Nodes Appear Different
While seeing lymph nodes is normal, certain changes in their appearance may warrant further investigation. These changes include an increase in size, a more rounded shape, or a loss of the central fatty hilum. Such alterations can be due to various reasons, some benign and temporary, others indicating a more serious condition.
Benign causes for altered lymph nodes are common. Infections or general inflammation can cause lymph nodes to temporarily enlarge as they fight off foreign invaders. This reactive enlargement can also occur after vaccinations, such as for flu or COVID-19, as the immune system activates. The swelling from a vaccine is a normal immune response and typically resolves within a few weeks to a couple of months. Other non-cancerous reasons include autoimmune diseases, certain bacterial infections, or reactions to silicone implants.
Conversely, certain features of lymph nodes may indicate a concern. An enlarged, rounded lymph node with a thickened outer layer (cortex) and a diminished or absent fatty hilum can sometimes be associated with cancer. This could indicate the spread of breast cancer to the lymph nodes or, less commonly, a lymphoma. These mammogram findings do not definitively diagnose cancer but indicate the need for further evaluation to determine the cause.
Next Steps and Further Evaluation
When lymph nodes appear different on a mammogram, healthcare providers will recommend additional steps to gather more information. The evaluation aims to distinguish between benign and more serious causes.
Often, the next step involves additional imaging, such as a targeted ultrasound of the axilla. Ultrasound provides a more detailed view of the lymph nodes, allowing radiologists to assess their shape, size, and internal structure, including the thickness of the outer cortex and the presence of the fatty hilum. In some cases, a breast MRI might also be recommended for a comprehensive assessment.
If imaging results remain unclear or suggest a concerning finding, a biopsy of the lymph node may be performed. This procedure involves taking a small tissue sample from the node for microscopic examination by a pathologist. Often, even after further evaluation, altered lymph nodes are found to be benign, providing reassurance. Your radiologist or doctor will discuss these results and guide you through any necessary follow-up care.