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

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 ¹⁸FDG 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 ¹⁸FDG-PET/CT imaging.

Results: In each of these patients, moderate ¹⁸FDG 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 ¹⁸FDG 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.