title: Mismatch Repair Proteins and Microsatellite Instability in Colorectal Carcinoma (MLH1, MSH2, MSH6 and PMS2): Histopathological and Immunohistochemical Study.
abstract: BACKGROUND
  Colorectal cancer (CRC) is one of the most common cancers worldwide. Microsatellite instability (MSI) is detected in about 15% of all colorectal cancers. CRC with MSI has particular characteristics such as improved survival rates and better prognosis. They also have a distinct sensitivity to the action of chemotherapy.
  
  
  OBJECTIVE
  The aim of the study was to detect microsatellite instability in a cohort of colorectal cancer Egyptian patients using the immunohistochemical expression of mismatch repair proteins (MLH1, MSH2, MSH6 and PMS2).
  
  
  METHODS
  Cases were divided into Microsatellite stable (MSS), Microsatellite unstable low (MSI-L) and Microsatellite unstable high (MSI-H). This Microsatellite stability status was correlated with different clinicopathological parameters.
  
  
  RESULTS
  There was a statistically significant correlation between the age of cases, tumor site & grade and the microsatellite stability status. There was no statistically significant correlation between the gender of patients, tumor subtype, stage, mucoid change, necrosis, tumor borders, lymphocytic response, lymphovascular emboli and the microsatellite stability status.
  
  
  CONCLUSIONS
  Testing for MSI should be done for all colorectal cancer patients, especially those younger than 50 years old, right sided and high-grade CRCs.
authors.affiliation: Faculty of Medicine, Cairo University, Cairo, Egypt.
authors.forename: Nour El Hoda S
authors.initials: NE
authors.lastname: Ismael
authors.affiliation: Faculty of Medicine, Cairo University, Cairo, Egypt.
authors.forename: Samar A
authors.initials: SA
authors.lastname: El Sheikh
authors.affiliation: Ahmed Maher Teaching Hospital, Cairo, Egypt.
authors.forename: Suzan M
authors.initials: SM
authors.lastname: Talaat
authors.affiliation: Ahmed Maher Teaching Hospital, Cairo, Egypt.
authors.forename: Eman M
authors.initials: EM
authors.lastname: Salem
keywords: Colorectal cancer; Immunohistochemistry; Lynch Syndrome; Microsatellite instability; Mismatch repair proteins