title: Four molecular subtypes of colorectal cancer and their precursor lesions.
abstract: BACKGROUND
  In addition to chromosomal instability and microsatellite instability (MSI), a third pathway, epigenetic instability, has been implicated in progression to colorectal carcinogenesis. CpG island methylator phenotype (CIMP) refers to a subset of colorectal cancers (CRCs) that occur through the epigenetic instability pathway and that are characterized by widespread hypermethylation of promoter CpG island loci, resulting in the inactivation of several tumor suppressor genes or tumor-related genes. Colorectal cancers can be classified into 4 molecular subtypes according to their CIMP and MSI statuses: CIMP+/MSI+, CIMP+/MSI-, CIMP-/MSI+, and CIMP-/MSI-. There are differences between Western (United States and European Union) and Eastern (Korea and China) populations in the number of CRCs that are MSI+, and in the number of MSI+ CRCs that are CIMP+.
  
  
  OBJECTIVE
  To review the clinicopathologic and molecular features of the 4 molecular subtypes of CRCs and their precursor lesions, and to emphasize geographic differences in CRCs between Eastern and Western populations.
  
  
  METHODS
  This article is based on the author's own experimental data and a literature review of relevant articles indexed in PubMed (US National Library of Medicine).
  
  
  CONCLUSIONS
  The 4 molecular subtypes of CRC that are defined by their CIMP and MSI statuses are characterized by their own distinct clinicopathologic and molecular features and precursor lesions. In particular, the clinicopathologic features of MSI+ CRCs differ depending on the CIMP status. Further understanding of the heterogeneity in CRC molecular pathways may help to explain the diverse morphologic features of CRCs.
authors.affiliation: Department of Pathology, Cancer Research Institute, Brain Korea 2nd Stage, Seoul National University College of Medicine, Korea. ghkang@snu.ac.kr
authors.forename: Gyeong Hoon
authors.initials: GH
authors.lastname: Kang
mesh_terms: D000230:Adenocarcinoma / Q000175:diagnosis / Q000235:genetics / Q000401:mortality; D000236:Adenoma / Q000175:diagnosis / Q000235:genetics / Q000401:mortality; D000368:Aged; D014408:Biomarkers, Tumor; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000235:genetics / Q000401:mortality; D018899:CpG Islands / Q000235:genetics*; D044127:Epigenesis, Genetic; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D007723:Korea / Q000453:epidemiology; D008297:Male; D053842:Microsatellite Instability; D008875:Middle Aged; D009154:Mutation; D011230:Precancerous Conditions / Q000175:diagnosis / Q000235:genetics / Q000401:mortality; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics; D015996:Survival Rate
chemical_list: D014408:Biomarkers, Tumor; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf