18F-FDG-Avid Lymph Nodes After COVID-19 Vaccination on 18F-FDG PET/CT.

A 68-year-old man with right cheek melanoma after resection underwent 18F-FDG PET/CT, which was unremarkable except for multiple FDG-avid subcentimeter but rounded lymph nodes in the left axilla. The patient had undergone a COVID-19 vaccination in the left arm 3 weeks prior. As under vaccinations have been documented to cause reactive FDG-avid lymph nodes, the nodes in our patient were considered benign, reactive to the COVID-19 vaccination. Although FDG-avid benign, reactive nodes have been an uncommon finding in the past, the upcoming surge in COVID-19 vaccinations makes this an important finding for the interpreting physician to consider and recognize.