Aspiration cytology of focal xanthogranulomatous pyelonephritis: a diagnostic challenge.

A case of focal xanthogranulomatous pyelonephritis presenting as a circumscribed mass in a functioning kidney of a young male is described. Clinical, radiological, and cytological features closely mimicked renal cell carcinoma leading to radical nephrectomy. Peroperative findings and gross pathological features also corroborated preoperative diagnosis. The final diagnosis was a histologic surprise. It is an uncommon entity with cortical location, no pelvic communication, and progressively destroying the kidney. It should be considered in the differential diagnosis of any mass lesion at any age during preoperative clinicoradiological and cytological evaluation. A correct preoperative diagnosis can save unnecessary nephrectomy.