Breast cancer screening or COVID-19 vaccination? Do both.

Lymph-node swelling after the coronavirus vaccine can complicate breast-cancer screening, but timing of a mammogram can make a big difference
March 12, 2021

As the greatest vaccination drive in history pushes ahead, an interesting wrinkle has emerged. The lymph-node swelling that’s part of the immune system’s healthy reaction to COVID-19 vaccines often shows up on routine breast-cancer screening scans. That’s complicating the work of breast-cancer specialists who factor in lymph nodes when determining whether breast cancer or other health problems may be at hand.

To learn more – and for an expert recommendation on how women should proceed – UCHealth Today touched base with Dr. Dulcy Wolverton, a CU School of Medicine radiologist and the section chief for Breast Imaging at UCHealth University of Colorado Hospital on the Anschutz Medical Campus. If you’re in a hurry, here’s the gist: get vaccinated as soon as you can. Here’s how to get vaccinated at UCHealth. Try to schedule your breast-cancer screening before your vaccination. If that’s not possible and you’re not at elevated risk for breast cancer, delay your breast-cancer screening until about three months after your final COVID-19 dose. If you’re at higher risk or have noticed a lump, come in for a screening.

A woman prepares to get a mammogram, which if possible, should be done before getting the COVID-19 vaccine or several months after.
Lymph-node swelling that’s part of the immune system’s healthy reaction to COVID-19 vaccines often shows up on routine breast-cancer screening scans. But breast-cancer screening and COVID-19 vaccination can coexist, and both save lives. Photo: Getty Images.

Why do swollen lymph nodes matter in breast-cancer screening?

Dr. Dulcy Wolverton: It can matter because swollen lymph nodes can mean a few things. We worry most about lymph nodes if they’re only on one side and they’re pretty enlarged because sometimes they can be a sign of breast cancer otherwise too small to be seen because of really dense breast tissue on that side.

Mammograms can also help spot other problems with a patient’s health. Sometimes we see lymph nodes that are swollen on both sides, and that can be a sign of lymphoma, and also metastases from other cancers such as melanoma and lung cancer. Lymph node enlargement can also be caused by various infections and also systemic diseases such as rheumatoid arthritis, systemic lupus erythematosus and sarcoidosis.

When did the impact of COVID-19 vaccination in mammograms become evident?

Wolverton: We started noticing it in January. It’s a known phenomenon that there was axillary (armpit-area) swelling and discomfort from the clinical trials of the Pfizer and Moderna vaccines. They both had a certain amount of reporting about how often this happened, but we don’t have the same information from the Pfizer and the Moderna trials. For instance, the Moderna vaccine trial found that, among patients who were asked if they had problems post-vaccination, about 12% of patients reported swelling or tenderness in the axilla after the first dose and about 16% after the second dose.

The Pfizer vaccine trial didn’t ask that question, but 58 more women reported axillary swelling or tenderness among those vaccinated than among those who got the placebo.

A photo of Dulcy Wolverton
Dr. Dulcy Wolverton

How often are you seeing vaccination-related lymph-node swelling among breast-cancer screening patients at UCHealth?

Wolverton: I did an informal poll of my breast-imaging colleagues, and we’re all seeing women with enlarged lymph nodes on screening mammograms at least a few times a week. The Society of Breast Imaging estimates that lymph-node swelling appears in about 11% of screening mammograms after vaccination.

We also do breast MRI screening for women who are high risk. If they’ve had a vaccination, we tend to see it – MRIs show more of the axilla than a mammogram does. We also see it on CT scans when we’re screening for lung and other cancers. So lymph-node swelling is not just showing up in mammography and breast imaging.

How do you handle patients who have been vaccinated for COVID-19 and whose scans show swollen lymph nodes?

Wolverton: Vaccination is like a false positive (that is, an incorrect indication of the presence of disease), and it’s causing quite a bit of consternation in the breast-imaging community right now because of COVID-19 vaccination. It’s hard for us to just ignore it. I can go into a patient’s medical record and see that she was vaccinated, when that was, and what side it was on because the lymph-node swelling happens on that side. If she had a vaccination, we’re less likely to be worried about it, so it’s becoming a known entity.

As far as how to approach breast-cancer screening patients who have been vaccinated, we don’t want to miss evidence of cancer seen in an abnormal-looking lymph node. But the lymph nodes themselves can help us rule out breast cancer. Reactive lymph nodes [lymph nodes swollen from vaccination] look a little different than metastatic [where cancer has spread] lymph nodes. Metastatic lymph nodes tend to be rounder and larger. Reactive lymph nodes are more diffusely swollen, but their architecture is preserved.

We can use various signs to conclude that the lymph-node swelling is more likely to be reactive. If we don’t have any evidence of breast cancer from the mammogram, and we know that there’s been a recent COVID-19 vaccination, we can say “this is probably benign.” But we’re going to follow it, so we recommend that the patient come back in three months so we can take another look with ultrasound and make sure that the lymph-node swelling is going away.

On the other hand, if the lymph-node swelling isn’t on the same side that the patient received the vaccine, we can’t make that same assumption. We’ll then call the patient back, do an ultrasound, and, if it looks suspicious, do a biopsy.

Should a woman delay her mammogram for COVID-19 vaccination or delay vaccination for her mammogram?

Wolverton: Don’t put off the vaccination. UCHealth patients using My Health Connection will find guidance in the app about COVID-19 vaccination and mammogram scheduling. The ideal is that you have your mammogram before the vaccination. Then you’re good. But life isn’t that simple, and it doesn’t always work that way. So we suggest that you try to wait a month or so after the second vaccination – and, if it works for you, ideally three months.

But if you have a problem or spot a lump, do not delay. In any case, we certainly don’t want you to miss a full year, but you can typically delay for a few months and you’ll be just fine.

Does lymph-node swelling happen with other vaccines?

Wolverton: Yes. Pretty much anything that activates your immune system is going to by definition activate the lymph nodes on the side of injection. The worst one I’ve seen is the shingles vaccine. That really gets the lymph nodes going. Sometimes it happens with flu shots too.

Anything else you’d like to mention about mammograms and the COVID-19 vaccine?

Wolverton: I would emphasize that the lymph-node swelling we see with COVID-19 vaccination is not dangerous, that we know it’s happening, and that we’ve adapted our breast-cancer screening to coexist with vaccination. It’s a normal reaction to have lymph nodes that are swollen because you’ve been vaccinated. If you end up being called back in for a screening follow-up because of lymph-node swelling related to vaccination, it’s because we want to make sure that you are cancer-free. It can be a little bit confusing, I know, but it’s important to reassure women that, with a bit of flexibility, we can keep up the pace of vaccination and also spot breast cancers early. Doing both will ultimately save lives.

About the author

Todd Neff has written hundreds of stories for University of Colorado Hospital and UCHealth. He covered science and the environment for the Daily Camera in Boulder, Colorado, and has taught narrative nonfiction at the University of Colorado, where he was a Ted Scripps Fellowship recipient in Environmental Journalism. He is author of “A Beard Cut Short,” a biography of a remarkable professor; “The Laser That’s Changing the World,” a history of lidar; and “From Jars to the Stars,” a history of Ball Aerospace.