title: Diagnostic value of cytokeratin 7 and parvalbumin in differentiating chromophobe renal cell carcinoma from renal oncocytoma.
abstract: OBJECTIVE
  To investigate the diagnostic value of cytokeratin 7 (CK7) and parvalbumin at mRNA and protein levels.
  
  
  METHODS
  CK7 and parvalbumin mRNA expression levels in 23 oncocytomas and 32 chromophobe renal cell carcinomas (RCCs) were examined using gene expression microarrays. Immunohistochemistry was performed using monoclonal antibodies specific for CK7 or parvalbumin in 41 chromophobe RCCs and 55 oncocytomas.
  
  
  RESULTS
  CK7 mRNA was overexpressed in 18 of 32 chromophobe RCCs but only 3 of 23 oncocytomas. Parvalbumin mRNA was overexpressed in 15 of 32 chromophobe RCCs and only 4 of 23 oncocytomas. In contrast, CK7 mRNA underexpression was noted in 13 of 23 oncocytomas and only 6 of 32 chromophobe RCCs, while parvalbumin underexpression was seen in 14 of 23 oncocytomas but only 6 of 32 chromophobe RCCs. By immunohistochemistry, 27 of 41 (66%) chromophobe RCCs expressed CK7 diffusely compared to only 3 of 55 (5%) oncocytomas. Diffuse parvalbumin expression was seen in all 41 of 41 (100%) chromophobe RCCs and only in 26 of 55 (47%) oncocytomas.
  
  
  CONCLUSIONS
  Both mRNA and protein expression levels of CK7 appear significantly higher in chromophobe RCC compared to oncocytoma (p < 0.001). Parvalbumin expression is less specific but often displays a patchy pattern in oncocytomas. Our study provides further evidence that CK7 and parvalbumin immunostains may be useful in differentiating oncocytoma from chromophobe RCC in problematic cases. Negative or patchy staining (< 50% cells) for CK7 and/or parvalbumin strongly favors the diagnosis of oncocytoma.
authors.affiliation: Department of Pathology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois 60611, USA.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Adley
authors.forename: Veronica
authors.initials: V
authors.lastname: Papavero
authors.forename: Jun
authors.initials: J
authors.lastname: Sugimura
authors.forename: Bin T
authors.initials: BT
authors.lastname: Teh
authors.forename: Ximing J
authors.initials: XJ
authors.lastname: Yang
mesh_terms: D018249:Adenoma, Oxyphilic / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D000911:Antibodies, Monoclonal / Q000737:chemistry; D002292:Carcinoma, Renal Cell / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D003102:Colloids; D003937:Diagnosis, Differential; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D007501:Iron; D053552:Keratin-7; D007633:Keratins / Q000096:biosynthesis* / Q000235:genetics; D007680:Kidney Neoplasms / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D010320:Parvalbumins / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D012680:Sensitivity and Specificity
chemical_list: D000911:Antibodies, Monoclonal; D003102:Colloids; C507497:KRT7 protein, human; D053552:Keratin-7; D010320:Parvalbumins; D012333:RNA, Messenger; D007633:Keratins; D007501:Iron