Metanephric adenoma

A 59-year old woman was diagnosed with a tumour in her right kidney. A neph rectomy was performed, and a 45 mm diameter tan-pink coloured tumour was fo und. Microscopy revealed small, dark cells in organized arrays of small rou nd acini and tubules with glomeruloid infoldings. A diagnosis of metanephri c adenoma was made. The tumour cells proved diploid on flow cytometry and i mmunohistochemical staining was positive for CAM 5.2 and AE-3. FISH analysi s of three chromosomes did nor reveal any abnormal karyotype. It is importa nt to differentiate metanephric adenoma from renal cell carcinoma and adult Wilm's tumour, since it has a benign course.