A Rare Cause of False-Positive 18F FDG Uptake in Testicular Adrenal Rest Tumors Mimicking Malignancy in a Patient With Congenital Adrenal Hyperplasia

Testicular adrenal rest tumors (TARTs) are benign lesions believed to arise from pluripotent steroidogenic cells within the testes, typically developing under chronic stimulation by adrenocorticotropic hormone. We present the case of a male with congenital adrenal hyperplasia (CAH) who underwent FDG PET/CT due to bilateral testicular masses, demonstrating false-positive FDG avidity suggestive of malignancy. Following appropriate corticosteroid therapy, repeat imaging revealed complete metabolic resolution of the lesions. This case illustrates a rare false-positive finding on FDG PET/CT and to our knowledge, it is the first reported case demonstrating complete metabolic response on FDG PET/CT following an appropriate therapy in a patient with CAH-associated TARTs.