Swollen Lymph Nodes After COVID-19 Vaccines May Cause Mammogram Confusion

After you get a vaccine of any kind, including a COVID-19 shot, your lymph nodes—especially those under your arm—can get bigger as your immune system responds. While these enlarged lymph nodes are normal after a vaccine, they can sometimes be mistaken for malignancies on imaging tests like a mammogram.

Mammograms After COVID-19 Vaccines

An article published in the journal Clinical Imaging in January reported on four cases involving people who had anomalous readings on a mammogram after they got a COVID-19 vaccine.

In two cases, the person was having a regular screening mammogram, one person was having a follow-up mammogram for an issue with the breast, and the fourth person was being evaluated after feeling a lump in their left armpit. In all four cases, breast imaging showed enlarged or swollen lymph nodes in the armpit.

Three of the four people had received their first dose of Pfizer-BioNtech’s COVID-19 vaccine five to nine days before their mammogram. The fourth person had their first dose of Moderna’s vaccine 13 days before their mammogram.

In all four cases, the people had been vaccinated in the left arm and the enlarged lymph nodes were seen in the left armpit. None of the four people had a history of breast cancer.

Vaccines Can Cause Swollen Lymph Nodes

Dana Smetherman, MD, chair of the Commission on Breast Imaging with the American College of Radiology and chair of radiology at Oschner Health in New Orleans, tells Verywell that swollen lymph nodes after a vaccine are actually normal, and “a sign our body is producing an immune response.”

“It usually shows up within two to four days after the vaccine and can last up to 10 days,” Smetherman says. If a person gets a mammogram in that time, the enlarged glands can show up because some of the tissue under the arm is captured by the image.

Enlarged lymph nodes can also happen after other vaccinations, such as the HPV vaccine or flu shots, but Smetherman says the situation with COVID-19 vaccines is a little different “because we’re all getting this vaccine together at the same time.”

More People Getting Vaccines

In December, the Biden Administration announced its goal of administering 100 million COVID-19 vaccines during its first 100 days. According to the Centers for Disease Control and Prevention’s COVID-19 Vaccine Tracker, 64,177,474 doses have been administered in the U.S. as of February 22.

Many people getting a vaccine will also have a mammogram scheduled within days or weeks of their shot. This has created a somewhat unusual situation—before the pandemic, it would have been less likely for someone to have a vaccination and a mammogram close together.

Clinicians Must Stay Abreast of Vaccine Side Effects

The authors of the case report study said that radiologists should keep the potential side effect of the vaccine in mind when viewing breast images.

Clinicians will need to determine if a patient has recently been vaccinated at the time of the mammogram to ensure that appropriate follow-up care is conducted as well as avoid unneeded invasive tests like a biopsy of the lymph nodes.

Don’t Delay Your Shot—or Your Mammogram

“It is very important to stress that this is not a reason to delay the vaccine or to delay the screening mammogram,” Smetherman says. “We want lots and lots of people to get these vaccines.”

Even still, many people did not get a mammogram or other preventive care last year, citing concerns about the pandemic. “We may have been quarantining, but diseases like breast cancer were not,” Smetherman says.

If possible, schedule an annual mammogram before you get vaccinated or wait to have a mammogram done four to six weeks after you get your second dose. If it’s not possible to stagger the scheduling, it’s important to still get your shot and your mammogram.

The Society of Breast Imaging has guidelines for what to do if an enlarged node or other changes in the lymph glands are seen on a mammogram. “If nothing else in the breast looks abnormal, what we do is schedule a follow-up ultrasonography of the breast in a month or two just to see if those swollen lymph nodes go away,” Smetherman says.

It’s also important to note that swollen lymph nodes can be a sign of many illnesses and are not specific to breast cancer or other inflammatory changes. Even if you don’t see an enlarged lymph node, it can often be felt. “If you happen to feel it a few days after you had your vaccine, I would wait a couple of weeks to see if goes away,” Smetherman says.

If your swollen node does not go away in a few weeks, let your healthcare provider know.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.