Cryptorchidism as a potential source of misinterpretation in 18FDG-PET imaging in restaging lymphoma patients

Abstract Purpose The estimated prevalence of cryptorchidism in young males is close to 2%. In oncological PET/CT studies, it might be difficult to recognize false-positive 18 FDG uptake due to an ectopic testis. Materials and methods In this pilot study, we report on three patients with lymphoma referred for assessment of response to treatment and in whom cryptorchidism was not known at the time of 18 FDG-PET/CT imaging. Results In each of these patients, moderate 18 FDG uptake corresponding to an ovoid mass in the inguinal canal was (or could has been) misinterpreted as a lymphoma-involved inguinal lymph node. Clues to avoid misinterpretation are discussed. Conclusion Moderate 18 FDG uptake in ectopic testes represents a potential source of false-positive at initial staging or evaluation of therapeutic response of lymphomas and other malignancies that needs to be recognized.