The Society for Breast Imaging (SBI) is recommending that women schedule their annual mammogram before they get the COVID-19 vaccine or delay screening until four to six weeks after receiving the vaccine.
The recommendation comes after increasing reports of a side effect following receiving the COVID-19 vaccine: swollen, abnormal-appearing lymph nodes in the armpit on the same side as where COVID-19 vaccines were administered.
Swollen lymph nodes under the arm, also known as axillary adenopathy, are not an uncommon side effect of receiving a vaccine. They’re temporary and are actually a good sign as far as immunity goes.
“In stimulating the immune system, vaccines will sometimes cause the lymph nodes because they are a critical part of that system,” says Deanna Attai, MD, a breast surgeon at UCLA Health.
But they can complicate the reading of a mammogram, say experts. Or worse, raise suspicion of a cancer that isn’t there.
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A Puzzling Trend Takes Shape
The trend started to become apparent in early January, as vaccinations began. The SBI started hearing from members that in their clinical practices they were seeing enlarged lymph nodes on the same side in which people had received their vaccine.
“We started seeing multiple patients in succession with axillary adenopathy, raising suspicion that something was amiss,” says Katerina Dodelzon, MD, a diagnostic radiologist at Weill Cornell Medicine in New York.
Dr. Dodelzon adds, “Because the medical history is critical to what we do, particularly in radiology as it gives us a complete picture and allows us to make the most accurate diagnosis, we started asking questions and learned that every single one of these patients had received a recent vaccination in that same upper extremity.”
The Weill Cornell team quickly published a case series in the January 18 online edition of the journal Clinical Imaging, primarily to ensure that what was likely a reactive reaction would not be mistaken by radiologists for malignancies and result in unnecessary (and invasive) follow-up biopsies for women.
Since then, both the SBI and the Centers for Disease Control and Prevention (CDC) have reported that this side effect has occurred in 11.6 percent of clinical trial participants receiving the Moderna COVID-19 vaccine after the first dose and in 16 percent after the second dose.
The side effect appears less common in Pfizer-BioNTech trial participants receiving the vaccine, though a related side effect — lymphadenopathy (any swollen lymph node) — was reported in 1.1 percent of recipients in the arm or neck two to four days following vaccination.
But in that study, reports were volunteered, not solicited, so the SBI suspects that the incidence of adenopathy or lymphadenopathy was likely higher.
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New Guidelines Are a Precaution
The SBI is clear in stating that the COVID-19 vaccine itself does not increase the risk for cancer, and the new recommendations are precautionary, not a cause for alarm.
Lymph nodes are scattered throughout the body and act as a filter or clearinghouse for old or abnormal blood cells, as well as for bacteria, viruses, and even cancer, says Dr. Attai.
“When you get a cold or sore throat, the lymph nodes in the neck become swollen; this is a normal reaction to a viral or bacterial illness and is a sign that the immune system is doing its job,” she explains.
Lymph node swelling is not a side effect unique to the COVID vaccines and has likewise (but rarely) been reported following vaccinations for tuberculosis, herpes papillomavirus (HPV), and even the flu.
But it can confuse the picture for experts reading mammograms. “We only see this reaction on 0.02 to 0.04 percent of otherwise normal mammograms so it’s very, very rare. But up to 56 percent may be associated with malignancy, so as radiologists, we need to be sure that we don’t miss anything,” says Dodelzon, who coauthored the SBI recommendations.
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Women Urged to Self-Advocate
The rollout of the COVID-19 vaccines is starting to gain momentum across states, increasing the likelihood that more axillary adenopathies will be captured on routine mammograms.
While SBI is working diligently to ensure that its members are aware of reports of this side effect, and members themselves are working hard to ensure that vaccination questions are included on screening medical intake forms, the best advice is to be proactive and self-advocate.
“I don’t think that women need to be anxious and start performing self-axillary examinations,” says Dodelzon, “but they should inform the intake nurse or screening radiologist that they’ve had the Moderna or Pfizer (or possibly the Johnson & Johnson vaccine, which is under regulatory review) in the left or right arm.”
Attai cautions that women who choose not to postpone their screening mammograms and whose imaging shows this abnormality may still be called back within 4 to 12 weeks for ultrasound screening. This follow-up is simply to ensure that the lymph nodes have returned to normal size and appearance.