Fine-needle aspiration biopsy of gouty tophi: lessons in cost-effective patient management.

Gout, a disease resulting from the effects of hyperuricemia and a crystal-induced arthropathy, may produce soft tissue masses (tophi) which mimick neoplasia clinically and radiographically. We have recently diagnosed three cases of gouty tophus, two of which were clinically suspected to represent sarcomas, by fine-needle aspiration biopsy (FNAB) after extensive radiologic and clinical evaluation. There were two women and one man. aged 71, 73, and 50 yr, with palpable soft tissue masses that involved the right forearm, right hand, and right foot, respectively, Biopsies were obtained by using 25-gauge needles without the aid of general anesthesia. Morphologically, aggregates and disassociated slender, needle-shaped crystals were abundant and easily recognized on both Diff-Quik and Papanicolaou stains. By using a polarizing microscope with a first-order red compensator, the crystals showed negative birefringence, characteristic of sodium urate. Benign-appearing histiocytes, foreign-body-type giant cells, neutrophils, and amorphous debris were scattered among the diagnostic crystals. The diagnosis of gouty tophus can be easily established with FNAB in conjunction with compensated polarizing microscopy. Application of FNAB in the initial evaluation of appropriate soft-tissue masses provides a cost-effective diagnostic method, preventing more costly and often unnecessary clinical and radiologic tests.