Swollen lymph nodes, one COVID-19 vaccine side effect, could be misread as cancer, experts warn

Two mammograms
Two mammograms compare a patient’s breast days after receiving a COVID-19 vaccine, left, to a scan five years earlier. Swollen lymph nodes (top left) can look like cancer, unless radiologists know a patient’s vaccine history.
(Courtesy of Tenet Healthcare)

When the coronavirus pandemic caused life to grind to a halt last March, many men and women opted to temporarily delay routine medical procedures and preventive health screenings to limit their exposure to the virus.

Now that activities are beginning to resume, and as more Orange County residents receive COVID-19 vaccinations, it seems patients may finally be willing to pick up where they left off a year ago.

But a new confusion is arising as physicians are learning one possible side effect of the vaccine — enlarged lymph nodes — may interfere with the reading of mammograms and other radiologic imaging.

Dr. Jason S. Pang, a diagnostic radiologist for Placentia-Linda Hospital said some who’ve received their first dose of the COVID-19 vaccine may experience a swelling of their lymph nodes near the pit of the arm in which they received the vaccine shot.

The enlarged glands could be mistakenly perceived as an indication of cancer, particularly on mammograms, Pang said.

“When we see them only on one side, we may become concerned there could be some cancer in the breast on the same side,” he added. “We don’t want to unnecessarily call those patients back for an additional workup and cause undo anxiety.”

Jennifer Bayer, spokeswoman for Tenet Healthcare, which oversees Placentia-Linda Hospital as well as Fountain Valley Regional Hospital, said the issue recently came to a head when several women scheduled to receive mammograms suddenly canceled their appointments.

“When we chatted with people, we discovered there were some patients canceling mammograms out of confusion,” Bayer said. “If people are foregoing receiving the vaccine or canceling their mammograms — either way, that’s bad.”

Pang said swollen nodes were observed in 11.6% of patients aged 18 to 64 who had received a first-round dose of the Moderna vaccine. The incidence rose to 16% after the second dose, compared to 4.3% among a placebo group.

Studies revealed a much lower incidence of swelling among those who had received the Pfizer-BioNTech vaccine, just 58 cases more than the placebo group across the entire study, the radiologist added.

A panel of experts with the Society of Breast Imaging, in a Feb. 24 article published in the journal Radiology, put forth recommendations for managing responses to the vaccine-related swelling, or adenopathy, in radiology patients. Pang added some of his own advice.

  • Imaging should be performed prior to vaccination when possible.
  • Be sure to inform radiology personnel if you have recently received a vaccination and let them know what kind of vaccine was administered and in which arm.
  • If you’ve already received the first dose of the vaccine, do not put off getting your second because you have a mammogram or other radiology imaging appointment scheduled. Simply inform staff of the date of your first vaccination.
  • If you received your second vaccination shot and a mammogram or screening is not urgent, try and give yourself from four to six weeks before you book an imaging appointment.
  • Any feeling of swelling or tenderness in the armpit that lasts longer than four to six weeks after you’ve received a COVID-19 vaccination should be reported to a physician or health care provider.

“Clear and effective communication between patients, radiologists, referring physician teams and the general public should be considered of the highest priority when managing adenopathy in the setting of the COVID-19 vaccination,” SBI experts concluded in their report.

Pang said it is important for people who may have delayed screenings during the pandemic not to let fear of false readings keep them from taking preventive steps that could save their lives.

“We do want to emphasize to the public, as physicians, that screening is important,” he said. “Because so many women have put off their mammograms for more than a year, there are certain cancers that can develop.”

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