Case report of lymph node activation mimicking cancer progression: A false positive F18 FDG PET CT after COVID-19 vaccination.

This case illustrates a false positive F18 FDG PET CT in the left axilla of a woman being treated for metastatic breast cancer after COVID-19 vaccination. Follow-up ultrasound of the axilla indicated no metastasis, indicating that the lymphadenopathy was likely due to an immune response following vaccination. This case report, in conjunction with prior studies of other vaccines with similar findings suggest that providers should be aware of potential false positive imaging following COVID-19 vaccination. In light of these findings, clinicians and imaging providers should record the date and side of the vaccination and inform patient of potential false positive results to reduce patient anxiety and unnecessary tests as COVID-19 vaccines become widely available.