A Spontaneously Necrotic Wilms' Tumor Mimicking Renal Abscess: A Tricky Diagnosis not to Miss.

Wilms' tumor (WT) is the most common renal malignancy in children. Its clinical and radiologic presentation may mimic other pediatric renal diseases, including pyonephrosis or renal abscess. The authors report a case of a 3-year-old girl presenting with pyelonephritis and right renal mass suggestive of a renal abscess, not responding to antibiotics. Further investigations were conducted, including a percutaneous renal needle core biopsy. A stage I fully necrotic WT was finally diagnosed. This amazing case of a fully necrotic WT at diagnosis demonstrates the importance of anatomopathologic analyses in pediatric renal masses, even when the infection is suspected.