This 25 y/o female presented with a renal mass and underwent radical nephrectomy to rule out carcinoma. The specimen revealed xanthogranulomatous pyelonephritis with a large perinephric abscess. There is a 6.0 cm cavitary lesion in the center of the kidney lined by shaggy hemorrhagic surface. It communicates with the perinephric abscess on the central lateral aspect of the specimen. Case contributed by: Liang Cheng, MD, Dept. of Pathology, Indiana University School of Medicine, Indianapolis.