title: Natural history of small renal masses.
abstract: OBJECTIVE
  To review the natural history and growth kinetics of small renal masses (SRMs).
  
  
  METHODS
  The literature concerning natural history and growth kinetics of SRMs was collected from PubMed published from 1990 to 2014.
  
  
  METHODS
  We included all the relevant articles on the active surveillance (AS) or delayed treatment for SRMs in English, with no limitation of study design.
  
  
  RESULTS
  SRMs under AS have a slow growth potential in general. The mean linear growth rate is 0.33 cm/year, the mean volumetric growth rate is 9.48 cm 3 /year. The rate of metastasis during AS is below 2%. Some factors are associated with the growth rate of SRMs, including tumor grade, histological subtype, initial tumor size, age, radiographic characteristics, and molecular markers. No definite predictor of growth rate of SRMs is defined at present. SRMs with high tumor grade and the subtype of clear cell renal cell carcinoma may have aggressive growth potential.
  
  
  CONCLUSIONS
  AS is a reasonable choice for elderly patients with SRMs, who are at high risk from surgery. Progression during observation is the biggest concern while performing AS. There is no definite predictor of progression for SRMs under AS. Percutaneous renal biopsy providing immunohistological and genic biomarkers may improve the understanding of natural history of SRMs.
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Urology, Peking University First Hospital, Beijing 100034, China.
authors.forename: Xue-Song
authors.initials: XS
authors.lastname: Li
authors.forename: Li-Qun
authors.initials: LQ
authors.lastname: Zhou
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D018450:Disease Progression; D006801:Humans; D007680:Kidney Neoplasms / Q000473:pathology*