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Underarm Lump After COVID Shot Is Likely Lymph Swelling, Not Breast Cancer, Experts Say

MONDAY, March 1, 2021 -- That swollen lymph node under your arm could be a temporary side effect of a COVID-19 shot and not a sign of serious health problems.

Radiologists from Massachusetts General Hospital noticed an increase in patients with swollen underarm lymph nodes as they were doing routine mammogram screenings. So they established an approach to help prevent delays in both vaccinations and breast cancer screening.

When seen on mammograms, these vaccine-swollen nodes can be mistaken for those enlarged because of cancer. They may even lead to a biopsy.

"We had started to see more patients in our breast imaging clinic with enlarged lymph nodes on mammography, ultrasound and magnetic resonance imaging. And we noticed they were coming to our clinic after a recent COVID-19 vaccination," said lead author Dr. Constance Lehman, chief of breast imaging and co-director of the Avon Comprehensive Breast Evaluation Center at Mass General in Boston.

"We talked with our colleagues in primary care and in our breast cancer specialty clinics and realized we needed a clear plan for management," she said in a hospital news release.

The group's approach is based on three principles: The first is encouraging COVID-19 vaccination. The second is reducing or eliminating delays, cancellations and rescheduling of breast imaging. The third is avoiding unnecessary extra imaging or biopsies of lymph nodes that have become swollen from recent vaccination.

Lehman and colleagues said no additional imaging is needed for swollen lymph nodes after recent vaccinations unless swelling persists or the patient has other health issues.

This message should be communicated to both imaging staff and patients, they said.

Patient letters may read: "The lymph nodes in your armpit area that we see on your mammogram are larger on the side where you had your recent COVID-19 vaccine. Enlarged lymph nodes are common after the COVID-19 vaccine and are your body's normal reaction to the vaccine. However, if you feel a lump in your armpit that lasts for more than six weeks after your vaccination, you should let your health care provider know."

During the pandemic, screening mammograms and breast cancer diagnoses have declined sharply in many health care institutions, Lehman said. She said this may result in a surge in cancers diagnosed at later stages when it is harder to treat and an increased demand for cancer screening procedures as delayed tests are rescheduled.

"We believe our model can avoid reducing or delaying vaccinations and avoid further reduced or delayed breast cancer diagnoses based on confusion amongst patients and/or their providers," Lehman said.

The report was published online recently in the American Journal of Roentgenology.

© 2021 HealthDay. All rights reserved.

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