title: Analysis of papillary urothelial carcinomas of the bladder with grade heterogeneity: supportive evidence for an early role of CDKN2A deletions in the FGFR3 pathway.
abstract: OBJECTIVE
  The dual pathway model of urothelial carcinogenesis does not fully explain grade and stage progression in patients with initial low-grade, non-muscle invasive urothelial carcinomas. Fibroblast growth factor receptor 3 (FGFR3) mutations are a hallmark of the low-grade pathway, with subsequent progression to muscle invasion occurring when FGFR3 mutant tumours exhibit a homozygous CDKN2A deletion. We hypothesized that grade heterogeneity represents the morphological manifestation of molecular changes associated with disease progression.
  
  
  RESULTS
  We identified retrospectively 29 non-muscle invasive papillary urothelial carcinomas with grade heterogeneity (<20% high grade). Nineteen had sufficient material for immunohistochemistry, CDKN2A fluorescence in-situ hybridization and FGFR3 mutation analysis. Eight pure low-grade urothelial carcinomas (PLGUC) were also analysed. FGFR3 mutation was seen in 10 of 19 cases. A homozygous CDKN2A deletion was identified in the low-grade areas of eight of nine (88%) technically suitable FGFR3 mutant cases (including five pTa cancers), in five of nine FGFR3 wild-type carcinomas and in none of the PLGUC. Increased MIB-1 expression was seen in low-grade areas of 12 of 19, in high-grade areas of 17 of 19 cases with grade heterogeneity and in none of the PLGUC. p53 staining was increased in one of 19 low-grade and seven of 19 high-grade areas.
  
  
  CONCLUSIONS
  Our findings show that grade heterogeneity in urothelial carcinoma is characterized by increased MIB-1 labelling, and particularly in the FGFR3 mutant pathway, with homozygous deletions of CDKN2A in low- and high-grade areas. This would suggest that CDKN2A deletion occurs prior to grade progression and supports the current convention to assign the highest grade to urothelial carcinomas with grade heterogeneity.
authors.affiliation: Department of Pathology, University Health Network and Princess Margaret Cancer Center, Toronto, Canada.|Department of Anatomic Pathology, Sunnybrook Health Sciences Centre, Toronto, Canada.
authors.forename: Michelle R
authors.initials: MR
authors.lastname: Downes
authors.affiliation: Department of Pathology, University Health Network and Princess Margaret Cancer Center, Toronto, Canada.|Department of Urology, Erasmus MC, Rotterdam, the Netherlands.
authors.forename: Berber
authors.initials: B
authors.lastname: Weening
authors.affiliation: Department of Urology, Anthony Van Leeuwenhoek Hospital, Netherlands Cancer Institute, Amsterdam, the Netherlands.
authors.forename: Bas W G
authors.initials: BW
authors.lastname: van Rhijn
authors.affiliation: Department of Pathology, University Health Network and Princess Margaret Cancer Center, Toronto, Canada.
authors.forename: Cherry L
authors.initials: CL
authors.lastname: Have
authors.affiliation: Department of Pathology, University Health Network and Princess Margaret Cancer Center, Toronto, Canada.|Department of Radiology, Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: Kilian M
authors.initials: KM
authors.lastname: Treurniet
authors.affiliation: Department of Pathology, University Health Network and Princess Margaret Cancer Center, Toronto, Canada.
authors.forename: Theodorus H
authors.initials: TH
authors.lastname: van der Kwast
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002291:Carcinoma, Papillary / Q000235:genetics* / Q000473:pathology; D002295:Carcinoma, Transitional Cell / Q000235:genetics* / Q000473:pathology; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050763:Cyclin-Dependent Kinase Inhibitor p18 / Q000235:genetics*; D004252:DNA Mutational Analysis; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading / Q000379:methods; D051498:Receptor, Fibroblast Growth Factor, Type 3 / Q000235:genetics*; D012189:Retrospective Studies; D001749:Urinary Bladder Neoplasms / Q000235:genetics* / Q000473:pathology
chemical_list: C000614131:CDKN2A protein, human; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050763:Cyclin-Dependent Kinase Inhibitor p18; C496365:FGFR3 protein, human; D051498:Receptor, Fibroblast Growth Factor, Type 3
keywords: CDKN2A; FGFR3 mutation; MIB-1; bladder cancer; grade heterogeneity; grading