ABSTRACT
Metanephric adenoma is a very rare benign renal tumor; only 100 well-documented cases have been reported to date. Metanephric adenoma occurs at all ages, most commonly in the fifth and sixth decades. There is a 2 : 1 female preponderance. They appear to be benign tumors with no malignant potential, and their chief importance is related to the fact that they are most often misinterpreted as renal cell carcinoma or Wilms' tumor. Its light microscopic features are very characteristic, and imunohistochemical and electron microscopic studies are not critical to the diagnosis. We have experienced a case of renal tumor in a 44-year-old female patient diagnosed by ultrasonography-guided needle biopsy which showed small, tightly packed acini or tubular and papillary structures. The patient underwent right nephrectomy. We report metanephric adenoma diagnosed by ultrasonography-guided needle biopsy, which is a very rare and unique case.