title: Immunohistochemical analysis of SMARCB1/INI-1 expression in collecting duct carcinoma.
abstract: OBJECTIVE
  Collecting duct carcinoma (CDC) is a rare and aggressive renal tumor with a tendency to involve the renal sinus. CDC displays variable morphologic features that can overlap with those of renal medullary carcinoma. The loss of SMARCB1/INI1 tumor suppressor gene, initially found in pediatric malignant rhabdoid tumors of the central nervous system, kidneys, and soft tissues, was also recently described in renal medullary carcinoma. The current immunohistochemical study assessed SMARCB1/INI1 expression in a series of CDCs.
  
  
  METHODS
  A total of 20 archival cases of CDC were used to construct a tissue microarray. Each tumor was spotted 3-7 times; benign tissue from the same specimen was also included when available. The immunoexpression of SMARCB1/INI1 was evaluated using BAF47, a monoclonal mouse antibody directed against the SMARCB1/INI1 gene product. Nuclear staining was considered as indicative of SMARCB1/INI1 expression.
  
  
  RESULTS
  The complete loss of SMARCB1/INI1 expression was observed in 3 of 20 cases of CDC. Another 3 cases revealed focal and weak intensity staining. The remaining tumors showed multifocal or diffuse SMARCB1/INI1 expression with variable staining intensity. No significant differences were found in the clinicopathologic and outcome features regarding SMARCB1/INI1 status.
  
  
  CONCLUSIONS
  The complete loss of SMARCB1/INI1 immunoexpression was found in 15% of CDC. No differences were found between the SMARCB1/INI1 positive and negative cases regarding the clinicopathologic and outcome features. Our results suggest that some CDC cases might be associated with genetic alterations involving the SMARCB1/INI1 gene. In addition, SMARCB1/INI1 immunoexpression seems to be of limited value in the differential diagnosis of CDC versus renal medullary carcinoma, although these results require additional validation.
authors.affiliation: Department of Pathology, Johns Hopkins University, Baltimore, Maryland 21231-2410, USA.
authors.forename: Hillary
authors.initials: H
authors.lastname: Elwood
authors.forename: Alcides
authors.initials: A
authors.lastname: Chaux
authors.forename: Luciana
authors.initials: L
authors.lastname: Schultz
authors.forename: Peter B
authors.initials: PB
authors.lastname: Illei
authors.forename: Dilek E
authors.initials: DE
authors.lastname: Baydar
authors.forename: Athanase
authors.initials: A
authors.lastname: Billis
authors.forename: Rajni
authors.initials: R
authors.lastname: Sharma
authors.forename: Pedram
authors.initials: P
authors.lastname: Argani
authors.forename: Jonathan I
authors.initials: JI
authors.lastname: Epstein
authors.forename: George J
authors.initials: GJ
authors.lastname: Netto
mesh_terms: D000368:Aged; D002292:Carcinoma, Renal Cell / Q000737:chemistry* / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000032:analysis* / Q000096:biosynthesis; D004268:DNA-Binding Proteins / Q000032:analysis* / Q000096:biosynthesis; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007680:Kidney Neoplasms / Q000737:chemistry* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D000071796:SMARCB1 Protein; D014157:Transcription Factors / Q000032:analysis* / Q000096:biosynthesis
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D000071796:SMARCB1 Protein; C513266:SMARCB1 protein, human; D014157:Transcription Factors