Resolution of Misleading COVID-19 Vaccination-Related Nodal and Splenic FDG Uptake in the Follow-up Study

Newly diagnosed low-grade bilateral breast lymphoma in 63-year-old woman demonstrated intense FDG uptake in the left axillary lymph nodes and the spleen, concerning for lymphomatous involvement. Subsequent ultrasound-guided biopsy did not demonstrate any pathologic left axillary lymph nodes. Further investigation revealed COVID-19 vaccination in the left arm, 5 days prior to the 18 F-FDG PET/CT study. Six-month follow-up 18 F-FDG PET/CT showed resolution of the intense FDG uptake in the left axillary lymph nodes and spleen without any treatment, suggesting a self-remitting acute local and systemic immune response to COVID-19 vaccination.