Mammographic and sonographic findings in the breast and axillary tail following a COVID-19 vaccine

Axillary lymphadenopathy on breast imaging after recent coronavirus disease 2019 (COVID-19) vaccination has been reported in the literature as immunization has become more widespread. While muscle edema at the injection site has been observed on MRI secondary to an immune response, ipsilateral breast imaging observations of edema have not been reported to be seen with the COVID-19 vaccinations to date. Mammographic findings such as trabecular and skin thickening, along with increased echogenicity on ultrasound, can be seen with edema secondary to capillary leak or poor lymphatic drainage, and should be considered as a possible etiology for the observed breast edema following a recent COVID-19 vaccine. Inflammatory changes observed in the breast and axillary tail post vaccination described in this case series are transient, but clinically relevant for patients who experience swelling following injection. Similar to evaluations for suspected mastitis, a short interval imaging follow up to confirm resolution may be appropriate for patients with ipsilateral vaccination histories, and could potentially reduce the number of false positive examinations in this clinical scenario. However, inflammatory breast cancer can mimic inflammation and infection, therefore close follow up to resolution is critical as to not miss cancer.