title: One step nucleic acid amplification (OSNA) - a new method for lymph node staging in colorectal carcinomas.
abstract: BACKGROUND
  Accurate histopathological evaluation of resected lymph nodes (LN) is essential for the reliable staging of colorectal carcinomas (CRC). With conventional sectioning and staining techniques usually only parts of the LN are examined which might lead to incorrect tumor staging. A molecular method called OSNA (One Step Nucleic Acid Amplification) may be suitable to determine the metastatic status of the complete LN and therefore improve staging.
  
  
  METHODS
  OSNA is based on a short homogenisation step and subsequent automated amplification of cytokeratin 19 (CK19) mRNA directly from the sample lysate, with result available in 30-40 minutes. In this study 184 frozen LN from 184 patients with CRC were investigated by both OSNA and histology (Haematoxylin & Eosin staining and CK19 immunohistochemistry), with half of the LN used for each method. Samples with discordant results were further analysed by RT-PCR for CK19 and carcinoembryonic antigen (CEA).
  
  
  RESULTS
  The concordance rate between histology and OSNA was 95.7%. Three LN were histology+/OSNA- and 5 LN histology-/OSNA+. RT-PCR supported the OSNA result in 3 discordant cases, suggesting that metastases were exclusively located in either the tissue analysed by OSNA or the tissue used for histology. If these samples were excluded the concordance was 97.2%, the sensitivity 94.9%, and the specificity 97.9%. Three patients (3%) staged as UICC I or II by routine histopathology were upstaged as LN positive by OSNA. One of these patients developed distant metastases (DMS) during follow up.
  
  
  CONCLUSIONS
  OSNA is a new and reliable method for molecular staging of lymphatic metastases in CRC and enables the examination of whole LN. It can be applied as a rapid diagnostic tool to estimate tumour involvement in LN during the staging of CRC.
authors.affiliation: Department of Surgery, University of Erlangen-Nuremberg, Germany. roland.croner@uk-erlangen.de
authors.forename: Roland S
authors.initials: RS
authors.lastname: Croner
authors.forename: Vera
authors.initials: V
authors.lastname: Schellerer
authors.forename: Helene
authors.initials: H
authors.lastname: Demund
authors.forename: Claus
authors.initials: C
authors.lastname: Schildberg
authors.forename: Thomas
authors.initials: T
authors.lastname: Papadopulos
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Naschberger
authors.forename: Michael
authors.initials: M
authors.lastname: Stürzl
authors.forename: Klaus E
authors.initials: KE
authors.lastname: Matzel
authors.forename: Werner
authors.initials: W
authors.lastname: Hohenberger
authors.forename: Anne
authors.initials: A
authors.lastname: Schlabrakowski
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001483:Base Sequence; D015179:Colorectal Neoplasms / Q000473:pathology*; D017931:DNA Primers; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis / Q000175:diagnosis* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009696:Nucleic Acids / Q000737:chemistry*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D017931:DNA Primers; D009696:Nucleic Acids
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