[Metanephric Adenoma : A Report of Two Cases].

Metanephric adenoma is a rare benign renal epithelial tumor. We have experienced two cases of metanephric adenoma. The first case was a left renal tumor found by ultrasonography in a 26-year-old woman. The abdominal computed tomography (CT) revealed a 90 mm mass that was enhanced slightly in the early phase, and enhanced further in the late phase. Laparoscopic radical nephrectomy was performed with suspicion of renal cell carcinoma. The second case was a right renal tumor found by CT imaging for heart disease in a 64-year-old man. An abdominal CT revealed a 30 mm mass that was the same as our findings in the first case. Laparoscopic partial nephrectomy was performed with the suspicion of renal cell carcinoma. In both cases, tumor cells are positive for WT-1 and CD57 in immunohistochemical staining ; the final diagnosis was metanephric adenoma. It is difficult to differentiate metanephric adenoma from renal cell carcinoma by preoperative imaging ; the diagnosis depends on morphological and immunohistochemical profiles.