title: Microsatellite instability in poorly differentiated adenocarcinomas of the colon and rectum: relationship to clinicopathological features.
abstract: BACKGROUND
  Poorly differentiated adenocarcinomas of the colon and rectum (Por) feature the worst prognosis among the various types of colorectal carcinomas. Por is highly associated with microsatellite instability (MSI), although MSI is associated with an improved prognosis in colorectal cancers.
  
  
  OBJECTIVE
  To investigate the influence of MSI on clinicopathological features and survival of patients affected by Por.
  
  
  METHODS
  53 patients affected by Por were investigated. DNA extracted from tumour sections and the corresponding normal tissue was analysed by PCR at five microsatellite loci: BAT25, BAT26, D2S123, D5S346 and D17S250. Tumours with alterations at two or more loci were classified as MSI-Por. The others were classified as microsatellite stability (MSS)-Por. The clinicopathological features and survival of patients with MSI-Por and MSS-Por were investigated.
  
  
  RESULTS
  Of the 53 patients who were examined, 12 (22.6%) were MSI-Por, whereas 41 (77.4%) were MSS-Por. Significant differences were found between MSI-Por and MSS-Por regarding the following clinicopathological features: age, gender, lymph-node metastasis (MSI-Por: 4/12; MSS-Por: 33/41), TNM stage (MSI-Por: T1/T2/T3/T4 = 2/6/2/2; MSS-Por: 3/3/19/16) and lymphatic invasion (MSI-Por: 4/10; MSS-Por: 27/35). Kaplan-Meier survival curves and log-rank analysis showed that MSI-Por was associated with better prognosis than MSS-Por, although no significant difference was found.
  
  
  CONCLUSIONS
  Compared with MSS-Por, MSI-Por is significantly associated with a low incidence of lymph-node metastases and a low stage. This indicates that MSI-Por is a less aggressive subtype.
authors.affiliation: Department of Surgical Oncology, University of Tokyo, Tokyo, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kazama
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Watanabe
authors.forename: Takamitsu
authors.initials: T
authors.lastname: Kanazawa
authors.forename: Junichiro
authors.initials: J
authors.lastname: Tanaka
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Tanaka
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Nagawa
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology / Q000556:secondary; D000368:Aged; D000369:Aged, 80 and over; D002454:Cell Differentiation; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology; D004273:DNA, Neoplasm / Q000235:genetics; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D053842:Microsatellite Instability; D008875:Middle Aged; D009367:Neoplasm Staging; D011379:Prognosis; D016019:Survival Analysis
chemical_list: D004273:DNA, Neoplasm