Adolescent xanthogranulomatous pyelonephritis mimicking renal cell carcinoma on urine cytology: an atypical presentation.

Xanthogranulomatous pyelonephritis (XGP) is a chronic renal inflammatory lesion that is rarely diagnosed in children. We present a case of a 16-year-old boy presenting with gross hematuria and a lack of laboratory and radiographic findings for XGP who was suspected of having renal cell carcinoma on urine cytology. Left radical nephrectomy was performed, confirming the diagnosis of XGP. The cytologic mimicking of renal cell carcinoma by XGP emphasizes that physicians should consider XGP in the differential diagnosis. The inability of urine cytopathology to distinguish XGP from renal cell carcinoma suggests a need for the development of new pathology techniques.