Xanthogranulomatous pyelonephritis mimicking renal cell carcinoma: a case report

Introduction and importance: Xanthogranulomatous pyelonephritis (XGPN) is a rare, serious, and chronic inflammatory disorder of the kidney characterized by a destructive process that invades the renal parenchyma, which is most commonly associated with urinary tract obstruction and infection. It affects women more often than men. Case presentation: Herein, the authors report a case of a 48-year-old male presented to their hospital with complaints of malaise, fever, chills, left flank pain, and a history of a staghorn calculus in the renal pelvis, which was removed by surgery 7 years ago. Ultrasonography and computed tomography scans showed an enlarged left kidney with cystic formation and pelvicalyceal system dilation with the presence of multiple large stones. The renogram showed a dysfunctioning left kidney. An open radical left nephrectomy was performed. Renal cell carcinoma (RCC) was suspected in both the gross and microscopic examinations. The immunohistochemistry was the decisive factor in confirming the diagnosis of XGPN. Clinical discussion: Preoperative and postoperative diagnosis of XGPN can sometimes be difficult due to diverse differential diagnoses. The misinterpretation of ‘foam cells’ as ‘clear cells’ consistent with RCC is the most important diagnostic challenge for pathologists. Conclusion: The unusual findings of this case report suggest a careful evaluation of patients with a renal cystic mass, that can be misdiagnosed as a RCC. A combined computed tomography scan evaluation together with histopathology and immunohistochemistry are essential for a correct diagnosis of this rare renal entity.