After a COVID-19 vaccination, a person's underarm lymph nodes may become swollen on the same side of the body where they had the injection. That's normal. In fact, it's a sign that the immune system is responding to the vaccine. However, the swelling may also show up on mammogram images.
Breast imaging experts aren't surprised when it does.
"We've seen it before with other vaccines, such as the shingles vaccine (or) the flu vaccine," says Dr. Stamatia Destounis, a radiologist at Elizabeth Wende Breast Care in Rochester.
She says swollen lymph nodes resulting from a vaccine typically shrink back to their normal size within a few weeks.
That's why experts are urging women to separate their routine annual mammogram and any scheduled COVID-19 vaccination by several weeks.
"That would eliminate any confusion at the time of your screening mammogram because now we are reading the mammograms and we are frequently seeing some lymph nodes that may be enlarged," Destounis explains.
Ideally, Destounis says a mammogram should be scheduled before a vaccine appointment. If that's not possible, she says women should simply go ahead with their mammogram, even if it is within a few days of a vaccination.
Some women have already canceled or postponed their annual mammogram because of COVID safety concerns and Destounis does not want them to continue to put it off. But she also doesn't anyone to avoid the COVID-19 vaccine or cancel an existing appointment for the shot, because they can be hard to come by.
'We have a concern that if there is something there that needs to be found," she says. "By delaying mammograms even longer, that little something may turn out to be a bigger area of concern."
If swollen lymph nodes are detected in mammogram images, Destounis says an ultrasound may be ordered and the patient may be asked to come in for a follow-up screening in several months.