title: The findings of CT and MRI in patients with metanephric adenoma.
abstract: BACKGROUND
  Metanephric adenoma (MA) is a benign renal tumor that is difficult to distinguish from a malignant tumor via traditional radiography. The diagnosis of MA is often dependent on postsurgical histopathological examination. In the present report, the imaging features of MA on computer tomography (CT) and magnetic resonance imaging (MRI) were retrospectively evaluated.
  
  
  METHODS
  Eight MA patients, 17-67 years of age, were pathologically confirmed and recruited between April 2009 and November 2014. Four of the eight patients were female. All patients underwent CT scanning, and one patient underwent MRI scanning. Three patients underwent CTA of the renal arteries. All patients underwent resection surgery (radical nephrectomy in five and nephron-sparing surgery in three patients).
  
  
  RESULTS
  The average tumor size was 44.0 ± 23.6 mm. The lesions in 87.5 % cases were located both in the renal cortex and medulla and exhibited exophytic growth. Plain CT showed that MA tumors were solid, and the average CT value was 37.9 ± 6.7 HU. Dynamic contrast-enhanced CT revealed that enhanced degrees of MA tumors in the renal cortex, renal parenchymal, and pelvic phase were all lower than that of normal renal parenchyma. A slight enhancement in the renal cortex phase and an even higher enhancement in the renal parenchymal phase were observed in seven of the cases. Progressive enhancement in the pelvic phase was found in five cases and a slight decreased enhancement in the pelvic phase in two cases. MRI revealed that MA tumor was isointense on T1WI and isointense on T2WI with some slightly hyperintense areas in the center. CTA of the renal arteries revealed the nutrient artery in one patient and no nutrient artery in two. Immunohistochemical experiments demonstrated that most tumor cells were positive for vimentin, CK, and EMA.
  
  
  CONCLUSIONS
  MA is a rare benign renal neoplasm. Detailed knowledge of the CT and MRI characteristics of MA plays an important role in MA diagnosis and treatment.
authors: Department of MRI, the First Affiliated Hospital of Zhengzhou University, No.1 Jianshe East Rd, Erqi District, Zhengzhou, 450052, Henan Province, China.
authors: Jing
authors: J
authors: Yan
authors: Department of MRI, the First Affiliated Hospital of Zhengzhou University, No.1 Jianshe East Rd, Erqi District, Zhengzhou, 450052, Henan Province, China. chengjl@zzu.edu.cn.
authors: Jing-Liang
authors: JL
authors: Cheng
authors: Department of Pathology, the First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China.
authors: Chen-Fei
authors: CF
authors: Li
authors: Department of Radiology, the First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China.
authors: Yan-Bang
authors: YB
authors: Lian
authors: Operation Department, the First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China.
authors: Yuan
authors: Y
authors: Zheng
authors: Department of MRI, the First Affiliated Hospital of Zhengzhou University, No.1 Jianshe East Rd, Erqi District, Zhengzhou, 450052, Henan Province, China.
authors: Xue-Ping
authors: XP
authors: Zhang
authors: Department of MRI, the First Affiliated Hospital of Zhengzhou University, No.1 Jianshe East Rd, Erqi District, Zhengzhou, 450052, Henan Province, China.
authors: Chao-Yan
authors: CY
authors: Wang
mesh_terms: D000236:Adenoma / Q000000981:diagnostic imaging* / Q000473:pathology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed
keywords: Computer tomography; Magnetic resonance imaging; Metanephric adenoma; Pathology