Extra-articular knee lesion with high fluorodeoxyglucose-uptake on positron emission tomography
Synovitis, Pigmented Villonodular
Pigmented villonodular synovitis (PVNS) is an uncommon musculoskeletal tumor that is typically benign and often diagnosed radiologically by magnetic resonance imaging (MRI). Fluorodeoxyglucose (FDG)-uptake positron emission tomography (PET) is an imaging tool primarily used in oncology to evaluate malignancy. FDG measures metabolic activity with standardized uptake value (SUV). A high SUV is suggestive of malignancy. We report a case of PVNS detected incidentally by FDG-PET as an extracapsular mass adherent to vastus medialis tendon with a high SUV of 15.1. Given the patient's history of cancer and the high SUV, the lesion was initially considered a malignancy. The objective of this case report is to illustrate that even a high-SUV mass detected with PET imaging does not necessarily indicate malignancy, and thus a benign lesion can also demonstrate such elevated signal.