Metanephric adenoma of the kidney

Pediatric

metanephric adenoma with Fanconi–Bickel syndrome: a case report and review of literature. Radiological evaluation. A Renal ultrasound documented a sharply marginated peripheral hypoechoic hypovascular mass at the upper pole of the left kidney measuring 2 × 2 cm. B, C Computerized tomography scan of the abdomen showing a partially exophytic homogenously enhancing mass at the upper pole of the left kidney measuring 1.8 × 1.9 × 2 cm

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Retroperitoneal

laparoscopic partial nephrectomy for treatment of metanephric adenoma (Report of 6 cases). Preoperative CT scan. a Non-contrast CT scan results indicated that there was soft tissue density shadows in the lower-middle portion of the right kidney, with a clear boundary, a size of 4.2 × 3.8 cm and a CT value of 30–36 HU. b, c The density is uniform, and the enhancement degree of the tumor was significantly lower than that of the surrounding normal renal parenchyma

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Metanephric adenoma (MA) of the kidney is a type of benign renal neoplasm.

Epidemiology

While it can present at any age , the peak age of occurrence is thought to be around the 5 to 6 decades . There may be a 2:1 female preponderance .

Clinical presentation

Metanephric adenoma is asymptomatic in many patients. Some patients can have abdominal pain and hematuria.

Pathology

Metanephric adenoma is histologically characterized by the arrangement of monotonous small blue embryonal epithelial cells in an acinar, tubular, or sheetlike configuration. True cystic forms of metanephric adenoma are rare.

Abundant psammoma bodies are commonly found. There is some pathological overlap with that of Wilms tumors.

Immunochemistry may help in diagnosis and can show positivity to markers such as vimentin, pancytokeratin and cytokeratin-19 .

Associations

polycythemia: a characteristic finding seen in approximately 10% of patients with metanephric adenoma, promptly disappears after surgical resection.

Radiographic features

General

They are difficult to differentiate from other renal tumors such as renal cell carcinomas on imaging grounds . Metanephric adenoma however typically appears as a well-defined, unencapsulated, solitary solid mass.

CT

It commonly appears as a hyperattenuating mass on unenhanced CT; large tumors appear as heterogeneous, hypovascular masses with frequent foci of hemorrhage and necrosis. Calcification is seen in 20% of cases.