Presentation
Moderately tender mass near the patellar tendon.
Patient Data
Intermediate signal intensity mass with signal void rim (arrow) due to hemosiderin deposits. It shows muscle isointense signal on T1-weighted images and moderate enhancement after contrast injection.
Case Discussion
Circumscribed 5 mm mass in Hoffa's fat pad with peripheral signal voids due to susceptibility artifacts caused by hemosiderin deposits. The lesion was surgically excised. Histopathologic diagnosis: pigmented villonodular synovitis (PVNS).
Editor's note: Per the 2020 WHO Soft Tissue and Bone Tumors Classification (5th ed.), the recommended terminology is tenosynovial giant cell tumor with pigmented villonodular synovitis no longer recommended (although remains in common use).