Palatine tonsil SUVmax on FDG PET-CT as a discriminator between benign and malignant tonsils in patients with and without head and neck squamous cell carcinoma of unknown primary.

•Palatine tonsils with proven squamous cell carcinoma can have normal FDG uptake on PET-CT.•An SUVmax ratio between tonsils of greater than 1.6 had 100% positive predictive value for the presence of carcinoma.•The SUVmax ratio between tonsils in patients without tonsillar carcinoma is up to 1.5•Mild asymmetry in tonsillar FDG uptake can be seen in normal tonsils.