title: PAX-8 expression in renal tumours and distant sites: a useful marker of primary and metastatic renal cell carcinoma?
abstract: OBJECTIVE
  Immunohistochemical stains have greatly improved the diagnostic accuracy of renal cell carcinoma (RCC) for primary and distant tumours. We evaluate a marker that has recently been incorporated in clinical practice, PAX-8, in primary and metastatic RCCs.
  
  
  METHODS
  Two distinct tissue microarrays were used, one consisting of over 334 renal tumours, 294 with adjacent normal kidney and the other with 40 matched nephrectomy and metastatic sites of RCC. PAX-8 expression was assessed by a method of quantitative immunofluorescence.
  
  
  RESULTS
  PAX-8 was positive in 96% (146/152) of normal renal tissue and 83% (227/272) of renal tumours. PAX-8 staining was positive in clear cell, papillary and chromophobe tumours in 80% (165/207), 95% (39/41) and 100% (6/6) of samples, respectively. Overall, intensity of PAX-8 expression was significantly higher in RCC metastatic sites than in the primary site (p=0.0047), however, in matched sites there was no statistically significant difference in the proportion of positive versus negative specimens (p=0.274).
  
  
  CONCLUSIONS
  As the role of molecular markers expands in the diagnostic algorithm, this study confirms that PAX-8 expression is a useful diagnostic marker for RCC. PAX-8 expression was found in the primary tumour and distant sites. Compared with normal tissue and other histological types, clear cell RCC has lower PAX-8 expression and is less frequently positive, therefore, the lack of expression does not exclude a tumour of renal origin.
authors.affiliation: Division of Oncology, Department of Medicine, Yale School of Medicine, New Haven, Connecticut, USA.
authors.forename: Meaghan L
authors.initials: ML
authors.lastname: Barr
authors.affiliation: Division of Oncology, Department of Medicine, Yale School of Medicine, New Haven, Connecticut, USA.
authors.forename: Lucia B
authors.initials: LB
authors.lastname: Jilaveanu
authors.affiliation: Department of Pathology, Yale School of Medicine, New Haven, Connecticut, USA.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Camp
authors.affiliation: Department of Pathology, Yale School of Medicine, New Haven, Connecticut, USA.
authors.forename: Adebowale J
authors.initials: AJ
authors.lastname: Adeniran
authors.affiliation: Division of Oncology, Department of Medicine, Yale School of Medicine, New Haven, Connecticut, USA.
authors.forename: Harriet M
authors.initials: HM
authors.lastname: Kluger
authors.affiliation: Department of Urology, Yale School of Medicine, New Haven, Connecticut, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Shuch
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis*; D015153:Blotting, Western; D002292:Carcinoma, Renal Cell / Q000473:pathology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007150:Immunohistochemistry; D007680:Kidney Neoplasms / Q000473:pathology*; D009362:Neoplasm Metastasis / Q000473:pathology; D000072636:PAX8 Transcription Factor; D051761:Paired Box Transcription Factors / Q000096:biosynthesis*; D046888:Tissue Array Analysis
chemical_list: D014408:Biomarkers, Tumor; D000072636:PAX8 Transcription Factor; C083325:PAX8 protein, human; D051761:Paired Box Transcription Factors
keywords: RENAL CANCER; TUMOUR MARKERS; UROPATHOLOGY