Presentation
One year history of a right ankle mass.
Patient Data
Synovial based mass with lobulated margins around the right ankle involving both the anterior and posterior recesses of the ankle. The bulk of the mass is seen posteriorly.
Demonstrated are the following signal characteristics:
- T1WI: hypointense to muscle
- T2WI: hypointense to muscle
- GRE: susceptibility artifact (blooming)
- STIR and PD fat sat: heterogeneous but predominantly hyperintense
- T1 post contrast (gadolinium): homogeneous enhancement
Histopathology findings: poorly circumscribed lobulated neoplasm with an infiltrative growth pattern. Heterogenous tumor population made up of mononuclear cells, scattered multinucleate (osteoclast-type) giant cells, foamy macrophages and siderophages. Scattered larger mononuclear cells are also identified with a peripheral rim of hemosiderin.
Histology images contributed by Dr L. Mekoa and Dr D. Lakhoo.
Case Discussion
This case demonstrates diffuse intra-articular pigmented villonodular synovitis (PVNS). MRI is considered pathognomonic due to the low signal on T1 and T2 with blooming artifact on susceptibility weighted imaging. The diagnosis was confirmed by histology.
Case contributions also by Dr Thandi Buthelezi.
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