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.
QUESTION: How often is this happening, and specifically what have you seen at the University of Michigan?
ANSWER: "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 said.
Sometimes, it can also be a response to a vaccine, she explained.