Background: Metanephric adenoma (MA) is a relatively rare though well-described benign neoplasm of the kidney that is generally detected in adults and occasionally in children.
Case Report: We found this neoplasm in a 56-year-old female with right fl ank pain , fever and hematuria. Ulterasound, computed tomography were compatiblem with those of renal cell carcinoma. With a diagnosis of renal cell carcinoma left radical nephrectomy was performed. This large, well-circumscribed, solid, tan to gray tumor showed histologic similarity to developing metanephric tubular epithelium. It is composed of uniformly small epithelial cells forming tubules. Immunohistochemically, tumor cells showed positive immunoreaction for vimentin but was negative for pancytokeratin, CK7, CD56, EMA and CD10.Clinical follow-up revealed no evidence of recurrence after 1 year.
Conclusions: Morphologically, metanephric adenoma shares features with papillary renal cell carcinoma (particularly the solid variant) and the epithelial component of the epithelial type Wilms’ tumor. We reviewed previous article for using immunohistochemistery in differential diagnosis of metanephric adenoma. A panel includes CK7 and CD57 is better in differentiating papillary renal cell carcinoma (PRCC) from MA. WT1 may be useful in separating Wilms’ tumor from MA and PRCC but is not helpful in differentiating MA from PRCC.

Keywords: Kidney, metanephric adenoma, immunohistochemistery