Management of Unilateral Axillary Lymphadenopathy Detected on Breast MRI in the Era of Coronavirus Disease (COVID-19) Vaccination.

Vaccination is an established but uncommon cause of unilateral axillary lymphadenopathy. Early clinical experience with coronavirus disease (COVID-19) vaccination suggests that the approved COVID-19 vaccines cause a notably higher incidence of axillary lymphadenopathy on breast MRI compared to other vaccines. Guidelines are needed to appropriately manage MRI-detected unilateral axillary lymphadenopathy in the era of COVID-19 vaccination and to avoid biopsies of benign reactive nodes. This article examines the available data on vaccine-related lymphadenopathy and offers a basic strategy to assess axillary lymphadenopathy on MRI and to guide management. At our institution, we are adding questions regarding the date(s) and laterality of administration of COVID-19 vaccination to our intake form before all breast imaging examinations. We consider MRI-detected isolated unilateral axillary lymphadenopathy ipsilateral to the vaccination arm to be most likely COVID-19 vaccine-related if within four weeks of either dose. In these cases, we assess the lymphadenopathy as BI-RADS 3 and recommend a follow-up ultrasound be performed within 6-8 weeks after the second dose. These guidelines may be refined as we gain further data on the expected time-course of axillary lymphadenopathy post COVID-19 vaccination. Until that time, this management pathway will help avoid unnecessary biopsies of benign vaccine-related reactive lymphadenopathy.