Background: Pigmented villonodular synovitis (PVNS) is a benign neoplasm of large joints. It may follow a locally aggressive course. The cytologic features of this neoplasm have not been characterized fully.
Case: A 70-year-old male presented with a lump in the left ankle joint. The histopathologic diagnosis was pigmented villonodular synovitis. Review of the cytologic smears revealed clusters of round and ovoid, bland-looking cells along with siderophages and binucleated and multinucleated giant cells.
Conclusion: When interpreted in the clinical context, fine needle aspiration cytology may render a correct preoperative diagnosis of pigmented villonodular synovitis.