Fine-needle aspiration cytology of xanthogranulomatous pyelonephritis.

Fine-needle aspiration cytology of xanthogranulomatous pyelonephritis in a fifty-seven-year-old Japanese woman is reported. Foamy cells and cells showing a gland-like pattern originating from degenerative renal tubules were found in the aspirated smears. Multinucleated giant cells and cells with pale yellowish cytoplasm were seen in the imprint smears at operation. These findings were diagnostic for xanthogranulomatous pyelonephritis. The cytologic diagnostic differences among xanthogranulomatous pyelonephritis, well-differentiated renal cell carcinoma, and renal oncocytoma are also described.