To be well acquainted with FDG PET appearance of PVNS, which can often mimic soft tissue metastases.

A case report of pigmented villonodular synovitis (PVNS) in a patient with small bowel melanoma in a 73-year-old female who underwent a staging FDG PET scan after surgical resection of the primary will be presented. There was intense focal FDG accumulation in a soft tissue lesion in the left knee infrapatellar soft tissues anteriorly which was reported as a possible metastasis. No other metastases were detected on the whole body FDG PET scan. Following which the patient had x rays and MRI with gadolinium of...

Whole body FDG PET showed intense focal activity localising to soft rounded soft tissue mass in the left knee infrapatellar joint. The X ray showed rounded soft tissue density in the anterior joint space and with no definite underlying bone erosions were seen. MRI showed lobulated mass in the infrapatellar space anterior to the anterior cruciate ligament with T1 low, T2 low signal and heterogenous contrast enhancement.

PVNS presents as FDG avid mass and thus is a potential mimic for metastatic disease in a known case of cancer. Reporting specialists need to be aware that both melanomas and PVNS can be intensely FDG-avid and consider PVNS/ tenosynovial tumours as a potential differential diagnosis.

S. Smith: Nothing to disclose

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