Metanephric stromal tumor as a rare differential diagnosis of a renal mass in children - a case report.

This report presents the case of a benign metanephric stromal tumor that occurred in the kidney of a 5-year-old boy and in which differentiation from a nephroblastoma was successful. Radiological assessment played the decisive role in this case, as the low initial volume, a high apparent diffusion coefficient, and lack of rapid tumor growth were considered atypical for a nephroblastoma. The boy underwent successful kidney-preserving resection without neoadjuvant chemotherapy, and intraoperative contrast-enhanced ultrasound examination helped to accurately define the tumor margins. The case is reported to provide information on the radiological picture of pediatric metanephric stromal tumor.