Three-phase 99mTc-MDP bone scan in a case of pigment villonodular synovitis

Pigment villondular synovitis (PVNS) is a rare synovial condition. The nature of this disorder is usually characterized as benign; however, malignant transformation has also been reported. MRI is the diagnostic modality of choice in evaluating this entity, revealing low T1 and T2 weighted signals and blooming artifact on gradient echo sequences. Three-phase Tc-99m-MDP bone scan has been infrequently used to assess these lesions; and a varied pattern on three phase bone scans has been reported. In the present case, we report a case of diffuse type PVNS lesion of the knee, evaluated with three-phase Tc-99m-MDP bone scan. This lesion had a progressive nature. Flow and blood pool images revealed minimal activity in the lesion, with increased radiotracer uptake on delayed images. After surgical resection, the patient's diagnosis of a PVNS was confirmed. Although, the pattern of PVNS has been characterized as more prominent on vascular and blood pool images, other patterns such as limited arterial and venous perfusion, as observed in our case, is also possible. In addition, SPECT-CT, as in this case, provided valuable information regarding the extent of joint involvement.