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Learning that a mammogram showed enlarged lymph nodes may be worrying. In some cases, enlarged lymph nodes may be linked to breast cancer. In others, they may be enlarged because of an infection, an autoimmune condition, a recent vaccination, or another noncancerous cause.
In this article, we’ll explain what mammogram lymph node findings may mean, why it’s important for doctors to compare current and past mammograms, and what next steps are typically recommended.
What Are Lymph Nodes? Lymph nodes are small, bean-shaped structures that are part of the body’s immune system. They help filter a clear fluid called lymph, trapping bacteria, viruses, cancer cells, and other substances that could cause illness.
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Lymph nodes are located in clusters throughout the body, including the armpits — an area known medically as the axilla. Lymph nodes in this area are called axillary lymph nodes, and they help drain lymph fluid from the arm, breast, and chest wall.
Because part of the armpit is often seen on mammograms, radiologists frequently see lymph nodes during breast imaging.
What Do Normal Lymph Nodes Look Like on a Mammogram?When radiologists review mammogram images of normal lymph nodes, they look at size, shape, and internal appearance. Healthy lymph nodes are usually oval and have a fatty center called the hilum.
A lymph node that appears larger, rounder, or denser than expected or looks different from prior imaging may need more evaluation. However, an abnormal-looking lymph node doesn’t automatically mean cancer is present.
Enlarged lymph nodes can sometimes be a sign that breast cancer cells have spread to nearby lymph nodes. In fact, the lymph nodes under the arm are often the first place breast cancer metastasizes (spreads) outside the breast.
In some cases, doctors can see a suspicious area in the breast and enlarged lymph nodes at the same time. However, it’s also possible for breast cancer to spread to nearby lymph nodes even when the cancer isn’t visible on a mammogram.
When breast cancer is found in the lymph nodes but the original tumor can’t be detected by an exam or imaging tests, it’s known as occult breast cancer. Occult breast cancer is rare, making up about 0.3 percent to 1 percent of all breast cancer cases.
Although occult breast cancer is rare, it’s one reason doctors take unexplained enlarged lymph nodes seriously and may recommend further testing.
It’s important to remember that many people with enlarged lymph nodes on a mammogram don’t have cancer. The finding may simply mean that more information or testing is needed to find the cause and rule out cancer.
Many conditions can cause lymph nodes to enlarge without being cancerous. Knowing about these possible causes may help you feel less worried while you wait for more answers.
Infections involving the breast, chest skin, arm, or nearby tissues can cause lymph nodes to swell. Examples include mastitis, an infection of the breast tissue, as well as cellulitis, skin infections, or abscesses.
Infections that affect more of the body can also cause enlarged lymph nodes. One common example is mononucleosis (mono), which is usually caused by the Epstein-Barr virus.
Autoimmune diseases occur when the immune system mistakenly attacks healthy tissues. Conditions such as rheumatoid arthritis and lupus may cause enlarged lymph nodes.
Some vaccines can temporarily cause swollen lymph nodes, especially in the armpit on the same side as the injection. This has been commonly reported after COVID-19 vaccines and booster shots.
Enlarged lymph nodes may also be linked to HIV, tuberculosis, and sarcoidosis. Some cancers that affect the blood or lymphatic system, such as lymphoma or leukemia, can also cause enlarged lymph nodes.
Because there are many possible causes, healthcare providers usually look at your overall health history, symptoms, and imaging results before deciding whether additional testing is needed.
One of the most important parts of evaluating mammogram lymph node findings involves comparing current images with previous mammograms. Radiologists look at whether the lymph nodes have stayed the same size and shape or have become larger or changed in shape.
Stable lymph nodes that have looked the same over time are often less concerning than lymph nodes that are newly enlarged or changing.
If your mammogram shows enlarged lymph nodes, your doctor will decide on next steps based on their size and shape, whether they’ve changed since your last mammogram, and whether anything else in the breast looks concerning.
Sometimes the radiologist may request additional mammogram images, such as a diagnostic mammogram or 3D mammogram, to get a closer look at the area. These extra images may help show whether a finding is concerning or appears benign (noncancerous).
Depending on the results, your radiologist may recommend getting additional mammograms about every six months to monitor the lymph nodes for changes.
An ultrasound uses sound waves to create images of tissues inside the body. Ultrasound is often one of the most useful tools for evaluating enlarged axillary lymph nodes because it can show the node’s shape, cortex (outer layer), and fatty hilum in greater detail.
Doctors may recommend an ultrasound even when there are no suspicious findings in the breast on the mammogram. In some situations, your doctor may order other imaging tests like a breast MRI or CT scan if more information is needed.
If a lymph node appears suspicious, your doctor may recommend a fine needle aspiration biopsy (FNA). During an FNA, a thin needle removes a small sample of cells, while a core needle biopsy removes a small sample of tissue for testing.
A biopsy can determine whether cancer cells are present in the lymph nodes. Many lymph node biopsies are performed using ultrasound guidance, which helps the doctor place the needle accurately in the area being tested.
If your mammogram shows enlarged lymph nodes, be sure to tell your healthcare team about:
These details can help your healthcare team identify a possible cause and determine whether follow-up testing is needed.
Finding enlarged lymph nodes on a mammogram can feel scary, but it doesn’t automatically mean cancer. Infections, recent vaccines, and autoimmune conditions are some of the noncancerous reasons this can happen.
If your doctor recommends more testing, such as an ultrasound or a biopsy, these tests can help determine the cause. Following your healthcare team’s recommendations can help you get the information you need and understand what, if anything, should happen next.
On MyBCTeam, people share their experiences with breast cancer, get advice, and find support from others who understand.
Has your mammogram found an enlarged lymph node? What did your healthcare team recommend next? Let others know in the comments below.
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