A case of renal metanephric adenoma: Histologic, immunohistochemical and cytogenetic analyses

BACKGROUND: A unique case of metanephric adenoma of the left kidney is reported in a 61-year-old woman presenting with an incidental renal mass on ultrasonography. METHODS/RESULTS: On radiographic examination, the presence of hypovascular renal cell carcinoma was suspected and left radical nephrectomy was performed. The resected tumor, measuring 4.9 x 4.7 x 4.5 cm, was well-circumscribed and solid and its cut surface was tan-pink with foci of focal hemorrhage and cystic change. Microscopically, the tumor was composed of uniformly small acini with hyperchromatic round nuclei. Some acini were dilated and occasionally contained glomeruloid-like bodies and psamoma bodies. Immunohistochemically, tumor cells showed positive immunoreaction for vimentin, cytokeratin and Leu 7. Cytogenetically, the tumor did not show numerical aberrations of chromosome 7 or 17 by fluorescence in situ hybridization. CONCLUSIONS: The patient is alive without recurrence or metastasis 4 years after surgery. Metanephric adenoma must be differentiated from other renal tumors, particularly Wilms' tumor or low-grade renal cell carcinoma. Immunohistochemical and cytogenetic analysis may be helpful in difficult cases.