title: Proficiency of DNA repair genes and microsatellite instability in operated colorectal cancer patients with clinical suspicion of lynch syndrome.
abstract: BACKGROUND
  Lynch syndrome (LS) diagnosis is underestimated, and most of the patients remain undetected after colorectal resections. The study aims to assess the frequency of LS in patients undergoing surgical treatment for colorectal cancer (CRC).
  
  
  METHODS
  A total of 458 CRC patients were operated from January 2005 to December 2008. Positive CRC family history (FH) was present in 118 (25.8%) patients. Histologic sections were reviewed for microsatellite instability (MSI) criteria (Bethesda guidelines), immunohistochemical (IHC) analysis for MLH1, MSH2, MSH6, PMS2 proteins, through the avidin-biotin-peroxidase complex, MSI (BAT-25, BAT-26, NR-21, NR-24 and MONO-27) and BRAF somatic mutation.
  
  
  RESULTS
  Of the 118 patients with FH, 61 (51.69%) met at least one of the revised Bethesda criteria. IHC was abnormal in 8 (13.1%) and MSI in 12 patients (20%). BRAF was negative in all cases. MSI histopathological included: intratumoral lymphocytes (47.5%), expansive tumors (29.5%) mucinous component (27.8%) and Crohn's like reaction in (14.7%). There was an association between the revised Bethesda criteria with: sex, mucinous histology and Crohn's like reaction; MSI and IHC with PMS2 and MLH1. Revised Bethesda criteria 4 had 10.6 increased chances to display positive MSI. We have proposed a score to contribute as a practical tool in the diagnosis of LS.
  
  
  CONCLUSIONS
  The frequence of LS in resected CRC patients was 2.6%. The criterion 4 Revised Bethesda was associated more strongly with the presence of MSI.
authors.affiliation: 1 Department of Gastroenterology and Pathology, University of São Paulo School of Medicine, São Paulo, SP, Brazil ; 2 Hospital A.C. Camargo, São Paulo, SP, Brazil.
authors.forename: Isabella Nicácio
authors.initials: IN
authors.lastname: de Freitas
authors.affiliation: 1 Department of Gastroenterology and Pathology, University of São Paulo School of Medicine, São Paulo, SP, Brazil ; 2 Hospital A.C. Camargo, São Paulo, SP, Brazil.
authors.forename: Fábio Guilherm Caserta Maryssael
authors.initials: FG
authors.lastname: de Campos
authors.affiliation: 1 Department of Gastroenterology and Pathology, University of São Paulo School of Medicine, São Paulo, SP, Brazil ; 2 Hospital A.C. Camargo, São Paulo, SP, Brazil.
authors.forename: Venâncio Avancini Ferreira
authors.initials: VA
authors.lastname: Alves
authors.affiliation: 1 Department of Gastroenterology and Pathology, University of São Paulo School of Medicine, São Paulo, SP, Brazil ; 2 Hospital A.C. Camargo, São Paulo, SP, Brazil.
authors.forename: Juliana Magalhães
authors.initials: JM
authors.lastname: Cavalcante
authors.affiliation: 1 Department of Gastroenterology and Pathology, University of São Paulo School of Medicine, São Paulo, SP, Brazil ; 2 Hospital A.C. Camargo, São Paulo, SP, Brazil.
authors.forename: Dirce
authors.initials: D
authors.lastname: Carraro
authors.affiliation: 1 Department of Gastroenterology and Pathology, University of São Paulo School of Medicine, São Paulo, SP, Brazil ; 2 Hospital A.C. Camargo, São Paulo, SP, Brazil.
authors.forename: Renata de Almeida
authors.initials: Rde A
authors.lastname: Coudry
authors.affiliation: 1 Department of Gastroenterology and Pathology, University of São Paulo School of Medicine, São Paulo, SP, Brazil ; 2 Hospital A.C. Camargo, São Paulo, SP, Brazil.
authors.forename: Márcio Augusto
authors.initials: MA
authors.lastname: Diniz
authors.affiliation: 1 Department of Gastroenterology and Pathology, University of São Paulo School of Medicine, São Paulo, SP, Brazil ; 2 Hospital A.C. Camargo, São Paulo, SP, Brazil.
authors.forename: Sérgio Carlos
authors.initials: SC
authors.lastname: Nahas
authors.affiliation: 1 Department of Gastroenterology and Pathology, University of São Paulo School of Medicine, São Paulo, SP, Brazil ; 2 Hospital A.C. Camargo, São Paulo, SP, Brazil.
authors.forename: Ulysses
authors.initials: U
authors.lastname: Ribeiro
keywords: B-raf; Hereditary nonpolyposis colorectal cancer (HNPCC); immunohistochemical (IHC); lynch syndrome (LS); microsatellite instability (MSI)