title: Percutaneous Kidney Biopsy for a Small Renal Mass: A Critical Appraisal of Results.
abstract: OBJECTIVE
  We report the diagnostic accuracy of renal mass biopsy for a small renal mass (4 cm or less) and identify predictors of successful renal mass biopsy in a contemporary cohort of patients from 2 large tertiary referral centers.
  
  
  METHODS
  A total of 442 biopsies of renal tumors 4 cm or less at 2 tertiary centers between 2008 and 2015 were included in study. Biopsy outcomes (malignant, benign or nondiagnostic) and concordance rates between renal mass biopsy and final surgical pathology were determined. Univariate and multivariate logistic regression analyses were performed to identify factors indicative of nondiagnostic biopsy.
  
  
  RESULTS
  The initial biopsy was diagnostic in 393 cases (88.9%) and nondiagnostic in 49 (11.1%). Of diagnostic biopsies 76% revealed renal cell carcinoma and 24% were benign. Renal cell carcinoma histological subtyping and grading was possible in 90.2% and 31.3% of cases, respectively. A second biopsy was performed in 11 of the 49 nondiagnostic cases and a diagnosis was possible in 100%, including renal cell carcinoma in 10 and oncocytoma in 1. Small tumor size, cystic nature of tumors and biopsy during the initial years of the study were independent predictors of nondiagnostic biopsy. The rates of accuracy in identifying malignancies, histiotyping and 2-tier grading between renal mass biopsy and surgical pathology were 97.1%, 95.1% and 68.8%, respectively.
  
  
  CONCLUSIONS
  Renal mass biopsy for a small renal mass can be performed accurately. Nondiagnostic renal mass biopsy was common for smaller masses and cystic masses, and during the initial years of the study. A second biopsy should be considered in nondiagnostic biopsy cases.
authors.affiliation: Department of Urology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea; Department of Urology, Asan Medical Center, University of Ulsan College of Medicine (CS, JHH, CSK, HA, IGJ), Seoul, Korea.
authors.forename: Hwang Gyun
authors.initials: HG
authors.lastname: Jeon
authors.affiliation: Department of Urology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea; Department of Urology, Asan Medical Center, University of Ulsan College of Medicine (CS, JHH, CSK, HA, IGJ), Seoul, Korea.
authors.forename: Seong Il
authors.initials: SI
authors.lastname: Seo
authors.affiliation: Department of Urology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea; Department of Urology, Asan Medical Center, University of Ulsan College of Medicine (CS, JHH, CSK, HA, IGJ), Seoul, Korea.
authors.forename: Byong Chang
authors.initials: BC
authors.lastname: Jeong
authors.affiliation: Department of Urology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea; Department of Urology, Asan Medical Center, University of Ulsan College of Medicine (CS, JHH, CSK, HA, IGJ), Seoul, Korea.
authors.forename: Seong Soo
authors.initials: SS
authors.lastname: Jeon
authors.affiliation: Department of Urology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea; Department of Urology, Asan Medical Center, University of Ulsan College of Medicine (CS, JHH, CSK, HA, IGJ), Seoul, Korea.
authors.forename: Hyun Moo
authors.initials: HM
authors.lastname: Lee
authors.affiliation: Department of Urology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea; Department of Urology, Asan Medical Center, University of Ulsan College of Medicine (CS, JHH, CSK, HA, IGJ), Seoul, Korea.
authors.forename: Han-Yong
authors.initials: HY
authors.lastname: Choi
authors.affiliation: Department of Urology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea; Department of Urology, Asan Medical Center, University of Ulsan College of Medicine (CS, JHH, CSK, HA, IGJ), Seoul, Korea.
authors.forename: Cheryn
authors.initials: C
authors.lastname: Song
authors.affiliation: Department of Urology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea; Department of Urology, Asan Medical Center, University of Ulsan College of Medicine (CS, JHH, CSK, HA, IGJ), Seoul, Korea.
authors.forename: Jun Hyuk
authors.initials: JH
authors.lastname: Hong
authors.affiliation: Department of Urology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea; Department of Urology, Asan Medical Center, University of Ulsan College of Medicine (CS, JHH, CSK, HA, IGJ), Seoul, Korea.
authors.forename: Choung-Soo
authors.initials: CS
authors.lastname: Kim
authors.affiliation: Department of Urology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea; Department of Urology, Asan Medical Center, University of Ulsan College of Medicine (CS, JHH, CSK, HA, IGJ), Seoul, Korea.
authors.forename: Hanjong
authors.initials: H
authors.lastname: Ahn
authors.affiliation: Department of Urology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea; Department of Urology, Asan Medical Center, University of Ulsan College of Medicine (CS, JHH, CSK, HA, IGJ), Seoul, Korea. Electronic address: igjeong@amc.seoul.kr.
authors.forename: In Gab
authors.initials: IG
authors.lastname: Jeong
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy / Q000379:methods; D002292:Carcinoma, Renal Cell / Q000473:pathology*; D005260:Female; D006801:Humans; D007668:Kidney / Q000473:pathology*; D007680:Kidney Neoplasms / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D063868:Patient Outcome Assessment; D012189:Retrospective Studies; D047368:Tumor Burden; D055815:Young Adult
keywords: biopsy; carcinoma; diagnosis; kidney; pathology; renal cell