Doctors urge women to delay mammogram after COVID-19 vaccine Expert: Hold off on test for four to six weeks after shot

Soon after the Pfizer/BioNTech and Moderna COVID-19 vaccines came to market, doctors began to notice something different in the mammogram images of a small fraction of women who’d recently gotten their shots: enlarged lymph nodes.

Swollen lymph nodes under one arm can be a rare sign of breast cancer, and when doctors find that, they usually order more testing, and potentially a biopsy to rule out cancer, said Dr. Kimberly Garver, the director of breast imaging at the University of Michigan.

However, in these women, the lymph node swelling was a normal immune response to the vaccines, and wasn’t actually cancer.

It led the Society of Breast Imaging to issue a recommendation that women should consider scheduling their mammograms four to six weeks after the second dose of a COVID-19 vaccine to avoid abnormal mammogram screenings and unnecessary tests.

Garver spoke to the Free Press on Friday, answering questions about what causes this to happen, and what the discovery means for the millions of women in America who are getting COVID-19 vaccines.

“About the same time we got a notice from the Society of Breast Imaging that this was being seen across the country, we saw a few cases, just a handful of cases, where we did see enlarged lymph nodes on the same side as where they got their vaccine,” Garver said. “We’re not seeing as many cases as we thought we might. There have been no official studies, to my knowledge, published yet on the data. But anecdotally, we’re not seeing as many cases as we were concerned there might be. It’s probably on the order of a small, very small, percentage.”

“If we see swollen lymph nodes on the mammogram, most of the time it’s the body reacting to an infection or some sort of inflammation like arthritis that the patient may have,” Garver added.

Sometimes, it can also be a response to a vaccine, she explained.

“When any foreign substance enters your body, it’s the lymph nodes’ job to kind of protect the body,” Garver said. “And they swell and react in response to any foreign substance. When this happens, it’s telling us that the lymph nodes are doing their job and they are reacting to something foreign.”

When people receive vaccines, she said, lymph nodes swell as they mount an immune response to the perceived threat. This is normal and healthy, she said.

But swollen lymph nodes can point to a more serious condition — such as cancer — as well, she said. So doctors cannot write off swollen nodes as only a vaccine response.

“In a tiny percentage of cases, (swollen lymph nodes) could be an indication of cancer in the breast or cancer elsewhere in the body, such as lymphoma,” she said. “... So we’ll bring the patient back, and we’ll get more history to find out what’s going on.”