Metanephric adenofibroma, originally referred to as 'nephrogenic adenofibroma', is a rare, biphasic, and benign metanephric tumor.
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Epidemiology
Metanephric adenofibroma typically occurs in children and young adults with a mean age of 13 years 1,3.
Clinical presentation
Patients present with non-specific symptoms include hematuria, abdominal pain, hypertension, and polycythemia 6.
Pathology
Metanephric adenofibroma has both stromal and epithelial components. The stromal component consists of spindle cells with hyperchromatic nuclei, which resembles that of metanephric stromal tumor. Epithelial nodules contain inactive embryonic epithelium which is identical to the characteristics of metanephric adenoma. Metanephric adenofibroma can be differentiated from Wilms' tumor by its benign characteristic and low mitotic activity 1,4,5.
Radiographic features
Ultrasound
Ultrasound will demonstrate a well-defined, slightly hyperechoic mass in the affected kidney 3,4.
Computed tomography
Computed tomography will show a solid mass (varied in size) with clear boundaries, and no calcification or necrosis detected. Multiple patchy low-density areas may also be observed in the neoplasm 2,7.
Magnetic resonance imaging
Magnetic resonance imaging will show a hyperechoic mass with nodular infiltration and protrusion into the renal cortex of the affected kidney 3.
Treatment and prognosis
Treatment of metanephric adenofibroma is usually complete or partial nephrectomy. The majority of patients will have good prognosis due to the benign characteristic and low mitotic activity of the neoplasm.