46-year-old female with triple negative left breast cancer, disease free for three years. A, Axial fused 18-FDG PET/CT three years earlier with no concerning lymph node in the left axilla. B, Surveillance contrast enhanced axial chest CT showed new left axillary lymphadenopathy with fat stranding 15 days after the first Covid-19 vaccine. Further evaluation with PET/CT six days after the 2nd dose of vaccine, demonstrated, C, multiple enlarged hypermetabolic left axillary lymph nodes and, D, a hypermetabolic round shaped left supraclavicular lymph node in axial fused 18-FDG PET/CT images. E, A subtle wedge-shaped intramuscular hypermetabolism (white arrow) was also noted in this case, similar to first and third cases. Ultrasonography guided core needle biopsy was performed. F, On ultrasonography, axillary lymph nodes had thickened cortex while the supraclavicular lymph node demonstrated, G, thickened cortex with loss of normal fatty hilum. I, Hematoxylin and eosin staining under 40x magnification shows enlarged germinal center with interfollicular expansion by small lymphocytes. 100x magnification images show, J, prominent germinal center with tingible body macrophage and, K, reactive germinal center with expansion of interfollicular regions by small lymphocytes and focally prominent endothelial cells.