Doctors warn vaccine effect could confuse mammogram results

Over the past few weeks, radiologists at UPMC realized that several dozen patients flagged for abnormal mammograms because of swollen underarm lymph nodes had something in common: They had recently received the COVID-19 vaccine.

Swelling in underarm lymph nodes is a known side effect of the vaccine, occurring in about 10% of cases, said Dr. Margarita Zuley, chief of the division of breast imaging at UPMC. The concern, she said, is that swollen lymph nodes can also be a symptom of breast cancer. If seen on a mammogram, doctors will call the patient back for a follow-up appointment for further evaluation.

“We don’t want patients to be alarmed by that,” said Dr. Zuley. “We want patients to be aware that this can happen.”

To avoid unnecessary appointments and worry, UPMC is recommending that women should consider getting mammograms before receiving their COVID-19 vaccines, or to wait until four weeks after their second dose. Women who prefer to get a mammogram closer to their vaccine may do so, but doctors would like them to be aware of the possible complications.

“To us, this is about shared decision-making with the patients,” Dr. Zuley said. “We don’t want people to be afraid.”

That policy is in line with recommendations released last month by the Society for Breast Imaging, which also recommends that doctors now ask up front whether patients have recently received a COVID-19 vaccine.

Most patients should not be delaying mammograms because of the vaccine, said Dr. Zuley, but rather scheduling mammograms now, prior to getting the vaccine, so that they don’t have to deal with the possible conflict as the vaccine becomes more widely available. UPMC, which does about 90,000 mammograms a year in its Magee network in Allegheny and Butler counties, is working to open additional appointments in the event of increased demand.

Women who are receiving diagnostic mammograms because there is a sign of a possible problem, such as a lump, should not delay those mammograms, even if they are scheduled to be vaccinated against COVID-19.

Because the COVID-19 vaccine is still in such short supply, eligible patients should get the vaccine as soon as they can, Dr. Zuley said, and they should not delay their shot because of a mammogram.

Lymph nodes swell as the body prepares an immune response, Dr. Zuley said, and swollen lymph nodes can occur in reaction to an injury, such as a cut; due to a virus, such as the common cold; or because of an immune response to the COVID-19 vaccine. Swollen lymph nodes under the arm can also be a sign of breast cancer, and that’s why doctors will follow up even if the swelling is likely a result of the vaccine.

Swollen lymph nodes are more common after the Moderna vaccine, said Dr. Zuley, and side effects are more common after the second shot than the first. Swollen lymph nodes are not a common side effect of the flu vaccine.

Screening mammograms are recommended annually for women older than 40, and patients can schedule them eight to nine months after their last mammogram.

“Screening mammograms are very important, especially if the patient missed their mammogram last year, which a lot of patients did,” Dr. Zuley said. “Get in now, get your mammogram, get it over with.”