title: Sporadic colorectal carcinomas with low-level microsatellite instability in Korea: do they form a distinct subgroup with distinguished clinicopathological features?
abstract: BACKGROUND
  The biologic significance of low-level microsatellite instability (MSI) in colorectal cancers (CRCs) remains unclear. This study aimed to elucidate whether sporadic MSI-low CRCs in Korea displayed distinguished clinicopathological characteristics from microsatellite stable (MSS) and MSI-high CRCs.
  
  
  METHODS
  We consecutively enrolled 657 patients who underwent their first surgical resections for stage I-IV sporadic CRCs and compared their clinicopathological features and prognosis after resection according to MSI status (574 MSS, 30 MSI-low and 53 MSI-high CRCs).
  
  
  RESULTS
  When compared with MSS CRCs, MSI-low CRCs showed significantly more frequent association with poorly differentiated histology, mucinous carcinoma, and large tumour size. In addition, MSI-low CRCs demonstrated significantly less frequent lymph node metastasis and advanced tumour stage than MSS CRCs. When compared with MSI-high CRCs, MSI-low CRCs were significantly more frequently located in distal colon. Three-year overall and disease-free survival rates of MSS, MSI-low and MSI-high CRCs were 83.5%, 90.0% and 91.7% and 82.0%, 89.1% and 87.5%, respectively and neither demonstrated significant difference between three groups.
  
  
  CONCLUSIONS
  These results indicated that sporadic MSI-low CRCs in Korea displayed distinguished clinicopathological features and might form a distinct subgroup especially from MSS CRCs. Further large studies are required to evaluate the impact of MSI-low status on prognosis.
authors.affiliation: Department of Medicine, Sungkyunkwan University School of Medicine, Samsung Medical Center, Seoul 35-710, South Korea.
authors.forename: Young-Ho
authors.initials: YH
authors.lastname: Kim
authors.forename: Byung-Hoon
authors.initials: BH
authors.lastname: Min
authors.forename: Hyo Kyung
authors.initials: HK
authors.lastname: Choi
authors.forename: Sue Jin
authors.initials: SJ
authors.lastname: Kim
authors.forename: Kyoung-Mee
authors.initials: KM
authors.lastname: Kim
authors.forename: Jin Yong
authors.initials: JY
authors.lastname: Kim
authors.forename: Dong Kyung
authors.initials: DK
authors.lastname: Chang
authors.forename: Hee Jung
authors.initials: HJ
authors.lastname: Son
authors.forename: Poong-Lyul
authors.initials: PL
authors.lastname: Rhee
authors.forename: Jae J
authors.initials: JJ
authors.lastname: Kim
authors.forename: Jong Chul
authors.initials: JC
authors.lastname: Rhee
authors.forename: Ho-Kyung
authors.initials: HK
authors.lastname: Chun
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015179:Colorectal Neoplasms / Q000453:epidemiology / Q000235:genetics* / Q000401:mortality / Q000473:pathology*; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D007723:Korea / Q000453:epidemiology; D008207:Lymphatic Metastasis; D008297:Male; D053842:Microsatellite Instability; D008875:Middle Aged; D009367:Neoplasm Staging; D055815:Young Adult