Gouty tophus presenting as a soft-tissue mass diagnosed by fine-needle aspiration: a case report.

We present a case in which a primary diagnosis of gout was made by fine-needle aspiration. The patient had a right distal ulnar mass, and the initial clinical and radiological diagnoses were that of giant cell tumor of tendon sheath. While tophi are the hallmark of gout, they rarely undergo aspiration because of the known clinical history. This case demonstrates that a tophus may mimic a soft-tissue neoplasm. Whenever an aspiration yields amorphous or granular material, the cytopathologist should be aware of and consider gouty tophus as a diagnostic possibility and perform compensated polarized microscopy on the specimen smears.