Swollen lymph nodes, a common, harmless COVID-19 vaccine side effect can lead to mammogram confusion

ATLANTA - When your radiologist pours over your mammogram, Dr. Henry Krebs says, they are looking for a change.

"We're looking, is this different from what the patient looked like last year, is this different from what they looked like a couple of months ago," Krebs says.

Back in early 2021, after the first Americans started getting vaccinated against COVID-19, Krebs, a radiologist at Cancer Treatment Centers of America in Newnan, Georgia, says they began noticing a change: swollen lymph nodes in the armpits of patients who had been recently vaccinated.

"Some of them were clinically palpable, meaning you could feel them in their armpits," Dr. Krebs says.  "Lymph nodes are one of those signs that say, 'Hey, there could be cancer there.' I mean, there are a lot of different reasons why nodes get enlarged and are abnormal. But, certainly in the back of our mind, ruling out cancer is always number one."

So, he says, the swollen nodes often lead to more follow-up tests.

"They were scary looking, and a lot of patients, unfortunately, got biopsied," Krebs says. "Now, thankfully, they were normal, but we hate putting patients through invasive procedures when they really don't need it."

With time, Dr. Krebs says, they realized the COVID-19 vaccine and other vaccines can cause the lymph nodes to temporarily swell, usually in the arm where the injection was given.

So, to avoid confusion, Krebs says, they asked patients to wait 4 to 6 weeks after their shot before getting their yearly screening mammogram.

However, he says, the realized telling everyone to wait may take the same amount of time after their shots might not be a good fit, either.

"Everybody is different in how your body reacts to these vaccines and how the body really comes back to its normal baseline state," he explains.

Instead of waiting, Dr. Krebs says, get your mammogram on schedule.

"Just make sure that you inform the technologist who's obtaining the imaging that, 'Hey, look, I had this done a couple of weeks ago or a month ago or whatever," just to put that into your record," Krebs says.