Aggressive Squamous Cell Carcinoma Arising in Chronic Xanthogranulomatous Pyelonephritis: CT Imaging of a Rare Case with Hepatic Metastases

Xanthogranulomatous pyelonephritis (XGP) is a rare, severe form of chronic renal infection associated with long-standing urinary tract obstruction, most commonly due to staghorn calculi. Although considered a benign inflammatory condition, it may rarely be associated with or evolve into squamous cell carcinoma (SCC) of the renal pelvis, an aggressive malignancy with poor prognosis.
We report the case of a 55-year-old male with a history of urolithiasis who initially presented with left flank pain. Computed tomography (CT) demonstrated findings consistent with XGP in a non-functioning left kidney. Despite nephrostomy drainage and indication for nephrectomy, the patient was lost to follow-up. One year later, he returned with fever, purulent nephrostomy discharge, anorexia, and weight loss, with marked inflammatory syndrome. Follow-up CT revealed an infiltrative renal mass with heterogeneous enhancement and necrosis, extending beyond the kidney, associated with ureteral involvement, lymphadenopathy, and multiple hepatic lesions. Biopsy of a liver lesion confirmed metastatic squamous cell carcinoma. The patient was managed with urinary diversion and systemic chemotherapy.
This case highlights the potential for malignant transformation of untreated XGP into aggressive renal SCC. The presence of infiltrative masses, heterogeneous enhancement, and extrarenal extension on imaging should raise suspicion for malignancy. Early surgical management and close follow-up are essential to prevent disease progression and improve outcomes.