FDG uptake in axillary lymph nodes after vaccination against pandemic (H1N1)

To alert the imaging community to potential false positive findings related to current immunization programmes against H1N1 influenza virus. We reviewed 10 patients referred for positron emission tomography/computed tomography (PET/CT) who had undergone recent vaccination. All studies showed (18)F-fluorodeoxyglucose (FDG) uptake in the draining axillary lymph nodes close to the vaccination site, while low-dose CT revealed lymph nodes ranged between 0.5 cm and 1.2 cm at the same site. This potential pitfall in PET/CT should be borne in mind during current vaccination programmes.