When Scheduling Mammogram, Keep in Mind That Vaccine May Temporarily Affect Results

Toan Nguyen, MD

Screening mammograms have proven to save lives by detecting breast cancer at an earlier stage when treatments can result in cure. In fact, it is likely the most important tool in the fight against breast cancer.

During the height of the COVID-19 pandemic last year, screening mammograms were halted for several weeks due to concerns of exposure to COVID-19. After the restrictions were lifted, many women still had significant delays obtaining their annual mammograms. Fortunately, screening mammograms have fully resumed and recently, three COVID-19 vaccines have received U.S. Food and Drug Administration emergency authorization as millions of people around the country have received vaccinations. However, the vaccines can produce an unwanted – but temporary – finding in mammogram results.

Axillary adenopathy, or swollen armpit lymph nodes, is sometimes a sign of breast cancer, present in 0.02%-0.04% of screening mammograms. This finding is one of the ways doctors detect breast cancer. There are emerging reports that two of the available COVID-19 vaccines, manufactured by Pfizer and Moderna, can induce the lymph nodes in the armpit to swell, coincidentally around the same time period that women are obtaining their mammogram. As a result, this finding can be worrisome and confusing, as additional tests and biopsies may be recommended to rule out a new breast cancer vs. a potential side effect of the vaccine. Swollen axillary lymph nodes have been associated with other vaccines as well, such as the bacille Calmette-Guérin vaccine, influenza vaccines, and the human papillomavirus vaccine.              

Currently, the Society of Breast Imaging recommends for women without any breast or axillary symptoms to schedule screening mammogram exams prior to the first dose of a COVID-19 vaccination or 4-6 weeks following the second dose of a COVID-19 vaccination. However, diagnostic mammograms performed to monitor concerning breast symptoms, such as a new breast or armpit lump, nipple discharge, skin changes of the breast, or other concerning findings affecting the breast, should not be delayed, regardless of the timing of the vaccine. Appropriate workup is needed to rule out cancer as soon as possible.

Please let your mammogram facility know if you recently received a dose of the COVID-19 vaccine to provide a clinical context.

About the Author

Toan Nguyen, MD, is a Breast Surgeon and Director of Breast Oncology for Lakeland Regional Health. To make an appointment with Dr. Nguyen, please call 863.603.6565.