title: Do MSI-L sporadic colorectal tumors develop through "mild mutator pathway"?
abstract: BACKGROUND
  The mutator pathway implied in the development of colorectal cancer (CRC) is characterized by microsatellite instability (MSI). MSI tumors can be subdivided according to the level of instability: MSI-H (high), MSI-L (low) or stable MSS. MSI-H CRC displays a well described distinct phenotype, but the true biologic significance of MSI-L is still uncertain. The objective of this study was to further clarify if the MSI-L phenotype could reflect a distinct pathway of tumor development with a different clinical behavior.
  
  
  METHODS
  We analyzed the clinicopathological and genetic variables of 156 patients with sporadic CRC in relation with the level of MSI of the tumors.
  
  
  RESULTS
  We have found that MSI-L tumors are someway in the middle of MSI-H and MSS CRC, as they share some features with each of the other 2 subgroups: left side location, lower incidence of LOH at MSH2 as MSS and Dukes B (stage II TNM) like MSI-H. Moreover, MSI-L tumors show higher incidence of KRAS mutations.
  
  
  CONCLUSIONS
  We believe that MSI-L tumors could be considered a distinct phenotype that develops through a "mild mutator pathway."
authors.affiliation: Servicio de Cirugía, Hospital Central de la Cruz Roja San José y Santa Adela, Reina Victoria, Madrid, Spain.
authors.forename: Soledad
authors.initials: S
authors.lastname: Oliart
authors.forename: Cristina
authors.initials: C
authors.lastname: Martínez-Santos
authors.forename: Mariano
authors.initials: M
authors.lastname: Moreno-Azcoita
authors.forename: Carlos
authors.initials: C
authors.lastname: Cerquella
authors.forename: Nargisse
authors.initials: N
authors.lastname: Nejda
authors.forename: Lydia
authors.initials: L
authors.lastname: Daimiel
authors.forename: Daniel
authors.initials: D
authors.lastname: Iglesias
authors.forename: Antonia M
authors.initials: AM
authors.lastname: Fernández-Peralta
authors.forename: Juan J
authors.initials: JJ
authors.lastname: González-Aguilera
mesh_terms: D000368:Aged; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000401:mortality / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D018895:Microsatellite Repeats; D008875:Middle Aged; D051718:MutS Homolog 2 Protein / Q000235:genetics; D009154:Mutation; D010641:Phenotype; D011518:Proto-Oncogene Proteins / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras); D016019:Survival Analysis; D018631:ras Proteins
chemical_list: C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; C497172:MSH2 protein, human; D051718:MutS Homolog 2 Protein; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins