Metanephric adenoma of the kidney

Abstract

A case of a rare renal tumor showing characteristic histologic features is presented. The patient was a 54 year old female, whose renal tumor was incidentally detected on abdominal ultrasound (US) examination. Ultrasound, computed tomography and angiography findings were consistent with a diagnosis of renal cell carcinoma of the hypovascular type. Left nephrectomy was performed. The tumor, which measured 2.6 x 2.6 x 2.5 cm, was located in the left renal cortex, and had a uniformly whitish-yellow cut surface and well-defined margin. Histologically, the tumor was characterized by its monomorphous growth pattern and was composed of uniformly small cells arranged in a tubular or rosette-like pattern. The tumor cells had scant cytoplasm and the nuclei were small, round and regular. These histologic features resembled the epithelial elements of a metanephric hamartoma in the nephroblastomatosis complex in infants. However, there was no mitosis and cellular atypia was minimal, suggesting benignity. According to these histologic features, the diagnosis of metanephric adenoma was made. Its clinicopathologic features are discussed.

Metanephric adenoma of the kidney

“…Few ultrasound, CR or MRI findings have been described in the literature. However, the case reported by Nonomura et al 9 had findings similar to those of the present case; ultrasound revealed a hypoechoic mass with a small, irregurarly shaped hypoechoic area and non-contrast CT showed the tumor as an isodense mass that had increasing attenuation values after contrast medium infusion. Furthermore, the tumor was represented as an isointense mass on both T 1 -and T 2 -weighted MRI.…”

“…Furthermore, the tumor was represented as an isointense mass on both T 1 -and T 2 -weighted MRI. In the case reported by Nonomura et al, 9 a preoperative diagnosis of renal cell carcinoma of the hypovascular type was made according to these image findings. In the present case, there was no obvious sign of neovascularization of the tumor.…”

Metanephric Adenoma of the Kidney: Case Report and Review of the Literature

“…Hypodense mass in the T1 weighted image, sometimes slightly hyperdense on the T2 weighted image was reported [18,28], as well as an isointense mass on both T1 and T2 weighted MRI scans. [14,30]. The case presented here, even appeared hypodense on the T2 weighted images.…”

“…Ultrasound images of metanephric adenoma have been described as hyperechoic [20] as well as hypoechoic [14,18,30]. Only one case was reported where ultrasound demonstrated a cystic renal mass, similar to the case presented here [22].…”

“…Many of these tumors had been diagnosed previously as nephroblastoma or renal cell carcinoma (4) or have been published under different diagnoses but fitted in the histological image of Mostofi and Brisigotti [5]. Since 1995, 39 cases of tumors with the typical morphology have been reported under the term of metanephric adenoma [3,[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27].…”