COVID-19 vaccines and mammograms: 7 things to know

Could getting a COVID-19 vaccine affect the results of your mammogram or other diagnostic imaging exams?

Physicians at MD Anderson are seeing an uptick in mammograms and other diagnostic imaging exams showing potential findings that can be confused with cancer in patients who’ve recently received one of the mRNA COVID-19 vaccines from Pfizer-BioNTech and Moderna.

This is due to a common side effect of the COVID-19 vaccines: swollen lymph nodes.

“One hypothesis for why we’re seeing this so often in mammograms right now is because there is a large number of women being vaccinated in a short amount of time,” says Jessica Leung, M.D., professor of Diagnostic Radiology and deputy chair of Breast Imaging.

Johnson & Johnson’s adenovirus-based vaccine has only begun to be distributed, and people may or may not also see a similar response from this vaccine. Nevertheless, Leung expects that patients will need to heed the same timing considerations to avoid issues with their mammograms and other diagnostic imaging tests.

Here are seven things Leung wants you to know about lymph node swelling, the COVID-19 vaccines and timing your screening appointments.

Lymph nodes are one of your immune system’s first lines of defense.

Lymph nodes are part of your lymphatic system and the immune system. These small, bean-shaped glands contain white blood cells to fight off infection and disease, and filter foreign particles. When they’re activated, they trigger the body’s adaptive immunity to fight off unwanted antigens.

Lymph nodes can be found throughout the entire body, but clusters of lymph nodes are located in the neck, underarm, chest, abdomen and groin. The underarm contains approximately 20 to 40 lymph nodes, called axillary lymph nodes. When the body’s immune system detects the presence of foreign invaders, it triggers the production of white blood cells. The white blood cells in the lymph nodes increase and begin filtering foreign particles, causing them to swell.

Both of the mRNA COVID-19 vaccines may cause swelling in the lymph nodes.

Some people who receive a COVID-19 vaccine may experience swollen lymph nodes on the same side of the body where they received the injection. Leung notes that lymph node enlargement is a normal reaction to the COVID-19 vaccines, as well as other vaccines, such as those for influenza and HPV. In clinical trials for the Moderna vaccine, approximately 16% of patients between the ages of 18 and 64 and 8.4% of patients over 65 developed swollen lymph nodes within 2 to 4 days after either dose of the COVID-19 vaccine, according to the Centers for Disease Control and Prevention.

“While this may seem alarming, this lymph node swelling caused by the vaccine is benign,” Leung explains, who notes that it’s not yet known whether the newer adenovirus vaccine from Johnson & Johnson may also cause side effects that affect screening results.

Schedule your mammogram or other diagnostic imaging test before your first COVID-19 vaccine dose.

If you haven’t scheduled your screening or vaccine appointment, Leung recommends getting your breast cancer screening before you receive the COVID-19 vaccine. This is the best way to avoid the potential of developing enlarged lymph nodes before your imaging exam.

And, Leung adds, it doesn’t matter how far in advance of your vaccine you get your mammogram.

“You could have your mammogram done an hour before your vaccination and that would be OK because your body would not have been injected with the inciting agent and therefore wouldn’t have had a chance to mount an immune response that would influence your mammogram results,” Leung says.

If you’ve already been vaccinated, schedule your diagnostic imaging exam 6 to 10 weeks after your second COVID-19 vaccine dose.

 If you need a diagnostic imaging exam that includes axillary lymph nodes for routine surveillance and screening, talk to your doctor to see if it is medically appropriate to delay the exam for 6 to 10 weeks after your COVID-19 vaccination. Your body’s immune response to the vaccine may cause temporary enlargement of your axillary lymph nodes that will need to subside to avoid interfering with your imaging exam.

In some cases, you shouldn't delay your screening or COVID-19 vaccination.

If you are unable to reschedule either your vaccine or your mammogram or diagnostic imaging test, go ahead and keep both appointments.

“In this case, the important thing is to clearly communicate to your health care provider, radiologist and the person doing your diagnostic imaging test when and in which arm you received the vaccine,” Leung says. “This can help them avoid misinterpreting your results.”

If swollen lymph nodes appear, doctors will keep an eye on the swelling to make sure it’s benign.

“The best test is tincture of time,” Leung says. “We’ll wait a few weeks and see what happens with the swelling.”

Cancer survivors should ask to have the vaccine administered in the arm opposite of where the cancer is or was, if possible.

If you are a current or past breast cancer patient, ask to receive the vaccine in the arm opposite of  the side of your body where you had cancer. If you have cancer in your right breast, for instance, get the vaccine in your left arm. And, if you have cancer in your left breast, get vaccinated in your right arm. For women who have cancer in both breasts, talk to your doctor to see which arm would be medically appropriate.

This will help support your immune response and reduce the chances that swollen lymph nodes caused by vaccination show up on your mammogram. Enlarged lymph nodes can falsely affect cancer screening and diagnostic imaging results up to 6 weeks after vaccination.

The COVID-19 vaccines and screening exams save lives.

Cancer doesn’t stop for COVID-19, so it’s important not to put off your cancer screenings – or the opportunity get a COVID-19 vaccine. “Whether you currently have cancer or not, it’s important to continue your regular screenings so your doctor can catch any potential issues as early as possible, increasing your chances of successful treatment,” says Leung.

And, she adds, vaccination is vital for slowing the spread of COVID-19 and ultimately achieving herd immunity. Cancer patients are at increased risk for developing severe complications from COVID-19, and MD Anderson experts have determined that the COVID-19 vaccines are safe and recommended for former and cancer patients.

“We don’t want you to put off your vaccination or screening exams, but it is important to time them optimally and talk to your doctor if needed,” says Leung.

Request an appointment at MD Anderson online or by calling 1-877-632-6789.