18F-Fluciclovine-Avid Mediastinal Lymph Node Metastasis of Cutaneous Malignant Melanoma

A 63-year-old man with recent diagnosis of high-risk prostate adenocarcinoma was referred to our Nuclear Medicine Department for 18F-fluciclovine PET/CT to rule out metastasis in the setting of elevated serum prostate-specific antigen levels. The patient had previous history of nodular melanoma of the right cheek treated 6 years back with surgery and adjuvant radiation. Surveillance 18F-FDG PET/CT for melanoma 1 month back had revealed enlarged FDG-avid mediastinal para-aortic lymph nodes, which on endoscopic biopsy had revealed melanoma metastasis. On current fluciclovine PET/CT, the same enlarged para-aortic lymph nodes showed fluciclovine uptake, suggesting false-positive uptake.