[Nephroblastoma-like kidney adenoma: case report of an extremely rare kidney tumor].

The nephroblastoma-like adenoma of the kidney is an extremely rare tumor with similarities to the nephroblastoma (Wilm's tumor) of the adult. In the literature, different terms are applied to these lesions. We present the case of a 64-year-old woman who underwent a nephrectomy for suspicion of renal cell carcinoma. Histologically the tumor consisted of tubular and papillary formations of monomorphic tumor cells without mitoses or cell-atypias and showed no fibrous capsule. The differential diagnosis to the nephroblastoma of the adult was difficult. Immunohistochemically the tumor expressed the embryonic form of the neural cell adhesion molecule (N-CAM) interstitially and not in the epithelial tumor cell as seen in Wilm's tumor. For the biologic tumor-definition it is important to collect and follow these very rare cases.