Systemic Sarcoidosis Induced by Chemotherapy, Mimicking Metastatic Testicular Carcinoma with 18F-FDG PET/CT

A 34-year-old male patient who had left orchiectomy and received three cycles of chemotherapy for testicular mix germ cell carcinoma was referred for 18fluorine-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) for complaints of weight loss and fever. PET/CT showed multiple and progressive 18F-FDG uptakes in supra and infra diaphragmatic lymphatic regions, and multiple abnormal 18F-FDG uptakes were noted in the lytic formed skeletal lesions. Clinicians remain in doubt regarding the multiple metastatic lesions without elevated serum tumor marker levels (alpha-fetoprotein, beta-human chorionic gonadotrophin, CA19-9, and carcinoembryonic antigen). Biopsy of the lytic lesion in the iliac bone revealed granulomatous inflammation suggestive of sarcoidosis. Systemic prednisone at 20-40 mg/daily was started. 18F-FDG PET/CT images showed complete metabolic response to prednisone 8 months following the start of treatment.