An unexpected consequence of COVID vaccination may be false positive mammograms. Radiologists are reporting swollen lymph nodes in the armpit that are triggering concern during routine mammography (Journal of the American College of Radiology pre-print, March 1, 2021).
In normal times, such axillary adenopathy would trigger a breast biopsy. But both the Moderna and the Pfizer vaccines can cause swollen lymph nodes on the same side as the vaccination. As a result, these are more likely to be innocent vaccine reactions than indications of a cancer spreading out of the breast.
Hold Off on Biopsy Due to False Positive Mammograms
Radiologists are now recommending follow-up mammograms for many women with these findings, rather than immediate biopsy. In fact, some women may not even need additional imaging, if they and their radiologists are reasonably confident that the vaccine produced false positive mammograms.
Mammogram centers are exceptionally busy right now, as many women who would have had scheduled screenings last year opted to delay them due to the pandemic. The Society of Breast Imaging now recommends that women get their mammograms prior to vaccination if possible. If a woman has already been vaccinated, the Society suggests waiting four to six weeks after the second dose for a routine mammogram. That should minimize the risk of false positive mammograms.