title: Adult metanephric adenoma presumed to be all benign? A clinical perspective.
abstract: BACKGROUND
  In most documented literature, metanephric adenoma (MA) is described as a benign tumour. Nevertheless, the nature of MA remains unclear and the clinical criteria of different MA subtypes are not well established. In the present study, we investigated the clinicopathological characteristics of MA, especially those of the uncommon histological subtypes.
  
  
  METHODS
  A cohort study was performed on 18 patients with pathologically proven MA in our institute from January 2004 to June 2014. The patients' clinicopathological and radiological data were retrospectively analysed and evaluated with an emphasis on the corresponding subtypes.
  
  
  RESULTS
  The patient population had a female: male ratio of 1:1 and mean age of 50 years (range, 18-66 years). The mean tumour size was 3.9 cm (range, 1.4-9.0 cm). There were no pathognomonic radiological features that posed a challenge for a preoperative diagnosis of MA. Fourteen patients underwent radical nephrectomy, and the other four underwent partial nephrectomy. Three histological subtypes were observed: classic MA (n = 10), malignant MA (n = 2), and composite MA with coexistence of different malignant components (n = 6). Despite the presence of atypical histological features and malignant components among the patients, only one patient developed distant metastasis (median postoperative follow-up, 56 months; range, 30-86 months).
  
  
  CONCLUSIONS
  MAs are a heterogeneous group of neoplasms with different biological characteristics. The correct identification of this entity and its subtypes would facilitate stratification of optimal management protocols and accurate assessment of the prognosis.
authors.affiliation: Department of Urology, The second Hospital of Tianjin Medical University, Tianjin Institute of Urology, Tianjin, 300211, China. 797980@sina.com.
authors.forename: Gang
authors.initials: G
authors.lastname: Li
authors.affiliation: Hebei North University, Laboratory Medicine College, Zhangjiakou, 075000, China. 1146167111@qq.com.
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Tang
authors.affiliation: Department of Pathology, Affiliated Hospital of Jining Medical University, Jining, China. 1064786671@qq.com.
authors.forename: Renya
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Department of Urology, The second Hospital of Tianjin Medical University, Tianjin Institute of Urology, Tianjin, 300211, China. hualinsong1991@163.com.
authors.forename: Hualin
authors.initials: H
authors.lastname: Song
authors.affiliation: Department of Urology, The second Hospital of Tianjin Medical University, Tianjin Institute of Urology, Tianjin, 300211, China. 2845494825@qq.com.
authors.forename: Shumin
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Department of Urology, The second Hospital of Tianjin Medical University, Tianjin Institute of Urology, Tianjin, 300211, China. yuanjieniu@outlook.com.
authors.forename: Yuanjie
authors.initials: Y
authors.lastname: Niu
mesh_terms: D000236:Adenoma / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000601:surgery; D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging* / Q000451:nursing / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009392:Nephrectomy / Q000379:methods; D011379:Prognosis; D011859:Radiography; D012189:Retrospective Studies; D047368:Tumor Burden; D055815:Young Adult