title: New insights into the development and differentiation of the human anorectal epithelia. Are there clinical consequences?
abstract: OBJECTIVE
  The epithelial lining of the anorectum still raises discussions concerning the levels of transition between the various zones and leads to an incomplete understanding of the immmunoprofile of rectal carcinoma. Since the expression of cytokeratins depends on the epithelial cell-type and the parahox-gene CDX2 is important for the development of the colorectal epithelium, we investigated different cytokeratins and CDX2 in the anorectum of human prenatal stages and in adult normal and neoplastic anorecta.
  
  
  METHODS
  The differentiation and spatiotemporal distribution of the epithelial zones were examined in 33 human embryos and fetuses, in a 2-year-old child and four adults. In comparison, 17 specimens of ultralow rectal adenocarcinoma and 4 specimens of anal carcinoma were investigated. Monoclonal antibodies were directed against cytokeratin (CK) 18, 20, 7 and 14 and CDX2.
  
  
  RESULTS
  Due to the cytokeratin profile and to CDX2 expression, the different anorectal zones could already be differentiated in human prenatal life. We showed that anorectal epithelial differentiation including the squamous epithelia ran in a craniocaudal direction, and that the anorectal zone was a transitional zone between rectal zone and anal transitional zone where CK 7, 18, 20 and CDX2 are simultaneously expressed. All cases of rectal adenocarcinoma showed positivity for CK 18, 20 and CDX2, and three also labelled for CK 7, whereas CK 14 was only expressed in the cases of anal carcinoma.
  
  
  CONCLUSIONS
  Our results elucidate the connection between the prenatal pattern and the origin of the different types of anorectal carcinoma.
authors.affiliation: Division of Clinical and Functional Anatomy, Department of Anatomy, Histology and Embryology, Innsbruck Medical University, Innsbruck, Austria. helga.fritsch@i-med.ac.at
authors.forename: Helga
authors.initials: H
authors.lastname: Fritsch
authors.forename: Sarah
authors.initials: S
authors.lastname: Zehm
authors.forename: Romana
authors.initials: R
authors.lastname: Illig
authors.forename: Patrizia
authors.initials: P
authors.lastname: Moser
authors.forename: Felix
authors.initials: F
authors.lastname: Aigner
mesh_terms: D000328:Adult; D001003:Anal Canal / Q000196:embryology / Q000254:growth & development*; D001005:Anus Neoplasms / Q000473:pathology; D000071616:CDX2 Transcription Factor; D002675:Child, Preschool; D004847:Epithelial Cells / Q000166:cytology*; D004848:Epithelium / Q000196:embryology / Q000473:pathology*; D005333:Fetus / Q000166:cytology; D018398:Homeodomain Proteins; D006801:Humans; D012004:Rectal Neoplasms / Q000473:pathology; D012007:Rectum / Q000196:embryology / Q000254:growth & development*
chemical_list: D000071616:CDX2 Transcription Factor; C491270:CDX2 protein, human; D018398:Homeodomain Proteins