Background: Metanephric adenoma (MA) is a benign renal tumor that is difficult to distinguish from a malignant\ntumor via traditional radiography. The diagnosis of MA is often dependent on postsurgical histopathological\nexamination. In the present report, the imaging features of MA on computer tomography (CT) and magnetic\nresonance imaging (MRI) were retrospectively evaluated.\nMethods: Eight MA patients, 17ââ?¬â??67 years of age, were pathologically confirmed and recruited between April 2009\nand November 2014. Four of the eight patients were female. All patients underwent CT scanning, and one patient\nunderwent MRI scanning. Three patients underwent CTA of the renal arteries. All patients underwent resection\nsurgery (radical nephrectomy in five and nephron-sparing surgery in three patients).\nResults: The average tumor size was 44.0 Ã?± 23.6 mm. The lesions in 87.5 % cases were located both in the renal\ncortex and medulla and exhibited exophytic growth. Plain CT showed that MA tumors were solid, and the average\nCT value was 37.9 Ã?± 6.7 HU. Dynamic contrast-enhanced CT revealed that enhanced degrees of\nMA tumors in the renal cortex, renal parenchymal, and pelvic phase were all lower than that of normal renal\nparenchyma. A slight enhancement in the renal cortex phase and an even higher enhancement in the renal\nparenchymal phase were observed in seven of the cases. Progressive enhancement in the pelvic phase was found\nin five cases and a slight decreased enhancement in the pelvic phase in two cases. MRI revealed that MA tumor\nwas isointense on T1WI and isointense on T2WI with some slightly hyperintense areas in the center. CTA of the\nrenal arteries revealed the nutrient artery in one patient and no nutrient artery in two. Immunohistochemical\nexperiments demonstrated that most tumor cells were positive for vimentin, CK, and EMA.\nConclusions: MA is a rare benign renal neoplasm. Detailed knowledge of the CT and MRI characteristics of MA\nplays an important role in MA diagnosis and treatment.
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