Pediatric metanephric adenoma: case report and review of the literature.

Metanephric adenomas are rare benign renal neoplasms, uncommonly seen in the pediatric population. They are typically detected incidentally on imaging studies performed for unrelated clinical presentations. Preoperatively, the imaging appearance of this tumor overlaps with the appearance of more common and more aggressive renal neoplasms such as Wilms' tumor or renal cell carcinoma. We present a case of a pathologically proven metanephric adenoma, monitored preoperatively for approximately 5 years, prior to definitive nephrectomy. As the majority of solid renal masses are resected soon after they are detected, to the best of our knowledge, this case is the first to demonstrate the natural in vivo progression of a pathologically proven metanephric adenoma.