18F-FDG PET/CT and 68Ga-FAPI-4 PET/CT Findings of Bilateral Knee Osteoarthritis in a Patient With Uveal Malignant Melanoma.

We present the findings of 68Ga-FAPI-4 PET/CT and 18F-FDG PET/CT of a metastatic malignant melanoma patient with osteoarthritis. A 65-year-old woman with a history of metastatic uveal malignant melanoma was referred to 18F-FDG PET/CT for restaging after enucleation and chemotherapy. 18F-FDG PET/CT imaging showed high radiotracer uptake in liver metastases; additionally mild uptake due to osteoarthritis was observed in both knees. However, although 68Ga-FAPI-4 showed lower uptake in liver lesions, it showed a more prominent uptake in both knee joints compared with 18F-FDG.