Breast Inflammatory Change Is Transient Following COVID-19 Vaccination

A 60-year-old woman presented for routine screening mammography 5 days following the COVID-19 booster vaccination (Pfizer-BioNTech) in the left arm. A new, nonpalpable global asymmetry measuring 13 cm was noted in the left upper outer breast (Figure, A). Targeted US did not demonstrate any significant findings. No axillary lymphadenopathy was seen. The findings were thought to be inflammatory in etiology related to recent vaccination. The mammogram was assessed as probably benign (Breast Imaging Reporting and Data System [BI-RADS] category 3), with a short-term follow-up examination recommended in 2 months. The patient presented for follow-up mammography 2 months later, with interval resolution of the asymmetry (Figure, B).

A 60-year-old woman presented for mammography 5 days following the COVID-19 booster vaccination (Pfizer-BioNTech) in the left arm. (A) Mammogram with a mediolateral oblique view of the left breast demonstrates a new, nonpalpable asymmetry in the upper breast (arrow). This was thought to be inflammatory in etiology related to recent vaccination. The mammogram was assessed as probably benign (Breast Imaging Reporting and Data System [BI-RADS] category 3), with a short-term follow-up recommended. (B) Mediolateral oblique view from the patient's follow-up mammography 2 months later, with interval resolution of the asymmetry.

While ipsilateral axillary lymphadenopathy following COVID-19 vaccination is a well-documented and relatively common finding, ipsilateral breast findings appear to be relatively rare. To our knowledge, only a few cases have been published regarding ipsilateral breast edema seen on a mammogram following vaccination (1,2). Injection-site redness and swelling are known adverse effects of the COVID-19 vaccinations. Currently, there are no guidelines for ipsilateral breast findings following COVID-19 vaccination, but short-term follow-up rather than biopsy may be appropriate in the absence of other suspicious imaging findings or known cancer history.