Gouty tophi without hyperuricemia, an interesting case diagnosed by fine-needle aspiration cytology

Abstract

Gout is a disorder of uric acid metabolism characterized by deposition of monosodium urate crystals in joint spaces or soft tissues. Gouty tophi can be the presenting feature of gout and can occur despite normal serum uric acid levels. Periarticular nodules can be a diagnostic dilemma for both clinicians and radiologists. A 39-year-old man presented with a nontender, firm swelling in right medial malleolus. His serum uric acid level was normal. Computed tomography scan report gave a differential diagnosis of synovial sarcoma and pigmented villonodular synovitis. Fine-needle aspiration cytology from the swelling revealed abundant granular amorphous deposits with needle-shaped crystals in a background of chronic inflammatory infiltrate. Biopsy from the swelling demonstrated the presence of needle-shaped crystals in a radial arrangement along with foreign-body giant cells and histiocytes. On the basis of cytological and histopathological findings, a diagnosis of gouty tophi was rendered.