Magnetic resonance imaging (MRI) has become the principal tool for Wilms tumor (WT) assessment and follow-up. MRI and histopathologic findings were not congruent in 2 of the q30 scanned patients with renal masses (2008 to 2011). Three lesions thought to be WT on MRI were found to be a sclerotic nephrogenic rest (1), cystic renal dysplasia (1), and focal chronic pyelonephritis (1). The "typical" features suggesting nephroblastomatosis and WT on MRI are unreliable and such lesions require biopsy for histopathologic diagnosis, especially when nephron-sparing surgery is necessary to preserve renal function.