title: Grade heterogeneity in small renal masses: potential implications for renal mass biopsy.
abstract: OBJECTIVE
  Understanding the degree of phenotypic heterogeneity in a small renal mass may have implications for interpreting renal mass biopsy data. In this study we quantify nuclear grade heterogeneity in small renal masses.
  
  
  METHODS
  Our institutional renal mass database was queried for patients with T1a (less than 4 cm) renal masses stratified by the criteria of imaging diameter less than 2 cm or 2 cm or greater, clear cell or papillary histology, low grade (Fuhrman 1-2) or high grade (Fuhrman 3-4) with tissue available for review. Four consecutive specimens were chosen from each of the 8 strata for a total of 32. All specimens were reanalyzed and the highest Fuhrman grade present in each 10× powered field was recorded. A case was classified as heterogeneous if multiple grades were present and as discordant if the highest Fuhrman grade was present in less than 50% of the specimen.
  
  
  RESULTS
  A median of 5 slides (IQR 3.5-7.5) and 59, 10× powered fields (IQR 34-109) were examined per patient. Overall 26 samples (81.3%) were heterogeneous, including 15 of 16 (93.8%) high grade specimens. Among all cases 10 (31.3%) were discordant and of high grade specimens 4 (25%) were discordant. Median fraction of low grade tissue in high grade specimens was 38.9% (IQR 12.2-57.2).
  
  
  CONCLUSIONS
  The majority of small renal masses demonstrated considerable nuclear grade heterogeneity. The greatest degree of heterogeneity and discordance was observed in high grade tumors. One should consider these findings when interpreting renal mass biopsy data as the risk of under sampling high grade tumors may not be insignificant.
authors: The James Buchanan Brady Urological Institute and Department of Urology, The Johns Hopkins University School of Medicine, Baltimore, Maryland. Electronic address: Mark.ball@jhmi.edu.
authors: Mark W
authors: MW
authors: Ball
authors: Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors: Stephania M
authors: SM
authors: Bezerra
authors: The James Buchanan Brady Urological Institute and Department of Urology, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors: Michael A
authors: MA
authors: Gorin
authors: Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors: Morgan
authors: M
authors: Cowan
authors: The James Buchanan Brady Urological Institute and Department of Urology, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors: Christian P
authors: CP
authors: Pavlovich
authors: The James Buchanan Brady Urological Institute and Department of Urology, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors: Phillip M
authors: PM
authors: Pierorazio
authors: The James Buchanan Brady Urological Institute and Department of Urology, The Johns Hopkins University School of Medicine, Baltimore, Maryland; Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors: George J
authors: GJ
authors: Netto
authors: The James Buchanan Brady Urological Institute and Department of Urology, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors: Mohamad E
authors: ME
authors: Allaf
mesh_terms: D001706:Biopsy; D002292:Carcinoma, Renal Cell / Q000473:pathology*; D006801:Humans; D007668:Kidney / Q000473:pathology*; D007680:Kidney Neoplasms / Q000473:pathology*; D060787:Neoplasm Grading
keywords: biopsy; carcinoma; neoplasm grading; renal cell; risk