Inflammatory Mimicry: Epididymo-orchitis Masquerading as Malignancy on [18F]-FDG PET/CT Imaging

False positive findings in ¹⁸F-fluorodeoxyglucose positron emission tomography-computed tomography (¹⁸F-FDG PET/CT) scans can present challenges in the accurate diagnosis and staging of various conditions. We report a case of a 52-year-old male with known adenocarcinoma of the stomach who underwent total gastrectomy and chemotherapy and was referred for ¹⁸F-FDG PET/CT to rule out recurrence. ¹⁸F-FDG PET/CT showed a large FDG-avid lesion involving the entire right testicle mimicking testicular cancer or lymphoma. Further evaluation with ultrasonography revealed epididymo-orchitis, possibly of granulomatous etiology. Orchitis, an inflammatory condition of the testicles, can cause misleading results in ¹⁸F-FDG PET/CT imaging for cancer surveillance. Imagers should cautiously interpret PET/CT findings, considering clinical context, patient history, and additional imaging modalities to distinguish true malignancies from false positives.