title: Clear cell papillary renal cell carcinoma as part of histologically discordant multifocal renal cell carcinoma: A case report and review of literature.
abstract: BACKGROUND
  Multifocal renal cell carcinoma of different histological subtypes within a single kidney is rare. We report a recently classified clear cell (tubulo) papillary renal cell carcinoma as part of an unusual case of multifocal renal cell carcinoma of discordant histological subtypes.
  
  
  RESULTS
  A 57 year-old-man was found to have multiple renal tumors and cysts on imaging and underwent a laparoscopic left radical nephrectomy. Pathological review showed multifocal renal cell carcinoma (clear cell (tubulo) papillary, clear cell and papillary renal cell carcinomas and papillary adenomas). Morphology of clear cell papillary renal cell carcinoma was supported by immunohistochemical profile (CK7+, HMWK+, CAIX+, AMACR-, CD10-, TFE3-).
  
  
  CONCLUSIONS
  This is the first report of clear cell papillary renal cell carcinoma as part of multifocal renal cell carcinoma of different histological subtypes. Related lineage of clear cell renal cell carcinoma and papillary renal cell carcinoma is supported by the highest prevalence of their combination within multifocal renal cell carcinoma of different histological subtypes along with their molecular interconnection. Clear cell papillary renal cell carcinoma may be uniquely placed between clear cell and papillary renal cell carcinomas since it shows morphological features intermediate between clear cell and papillary renal cell carcinoma along with overlapping but unique immunohistochemical profile. Clear cell papillary renal cell carcinoma may be molecularly related to clear cell and papillary renal cell carcinomas since the tumors overexpress markers of HIF pathway activation with normal/elevated VHL mRNA expression and some tumors show losses of chromosome 3. Due to the overlapping morphology, it is possible that cases of clear cell papillary renal cell carcinoma may have been misclassified as papillary or clear cell renal cell carcinoma in the literature, incorrectly increasing their reported prevalence. Identification of multifocal RCCs may be related to the extent of pathological sampling.
authors: Department of Laboratory Medicine and Pathobiology, University of Toronto, Medical Sciences Building, 6th Floor, 1 King's College Cir, Toronto, ON, Canada M5S 1A8. Electronic address: shaotiff@gmail.com.
authors: Tiffany
authors: T
authors: Shao
authors: St. Michael's Hospital and Li Ka Shing Knowledge Institute, 209 Victoria St, Toronto, ON, Canada M5B 1T8. Electronic address: py_basketball@hotmail.com.
authors: Peter
authors: P
authors: Yousef
authors: St. Michael's Hospital and Li Ka Shing Knowledge Institute, 209 Victoria St, Toronto, ON, Canada M5B 1T8.
authors: Irina
authors: I
authors: Shipilova
authors: Department of Laboratory Medicine and Pathobiology, University of Toronto, Medical Sciences Building, 6th Floor, 1 King's College Cir, Toronto, ON, Canada M5S 1A8. Electronic address: rola.saleeb@mail.utoronto.ca.
authors: Rola
authors: R
authors: Saleeb
authors: St. Michael's Hospital and Li Ka Shing Knowledge Institute, 209 Victoria St, Toronto, ON, Canada M5B 1T8; Department of Surgery, University of Toronto, Canada. Electronic address: LeeJaso@smh.ca.
authors: Jason Y
authors: JY
authors: Lee
authors: Department of Laboratory Medicine and Pathobiology, University of Toronto, Medical Sciences Building, 6th Floor, 1 King's College Cir, Toronto, ON, Canada M5S 1A8; St. Michael's Hospital, 30 Bond St, Toronto, ON, Canada M5B 1W8. Electronic address: adriana.krizova@mail.utoronto.ca.
authors: Adriana
authors: A
authors: Krizova
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis; D002291:Carcinoma, Papillary / Q000473:pathology; D002292:Carcinoma, Renal Cell / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry; D007680:Kidney Neoplasms / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009378:Neoplasms, Multiple Primary / Q000473:pathology*
chemical_list: D014408:Biomarkers, Tumor
keywords: Clear cell papillary renal cell carcinoma; Molecular analysis; Multifocal histologically discordant renal cell carcinoma