title: Prognostic Impact of Microsatellite Instability in Colorectal Cancer Presenting With Mucinous, Signet-Ring, and Poorly Differentiated Cells.
abstract: OBJECTIVE
  Mucinous cells (MUCs), signet-ring cells (SRCs), and poorly differentiated cells (PDCs) are uncommon histologic types and have been associated with advanced tumor stage and poor prognosis. However, MUCs, SRCs, and PDCs are commonly observed in cancers with high microsatellite instability (MSI), which have favorable outcomes compared with cancers with microsatellite stability (MSS). The purpose of this study was to evaluate the prognostic impact of high-MSI in patients with sporadic colorectal cancer presenting with MUCs, SRCs, and/or PDCs.
  
  
  METHODS
  Between January 2006 and December 2012, 176 with proven microsatellite status who also presented with MUCs, SRCs, and PDCs were selected for this study and were divided into 2 groups, high-MSI and MSS; their outcomes were analyzed.
  
  
  RESULTS
  Of the 176 patients, 56 and 120, respectively, had high-MSI and MSS cancers. High-MSI cancers had larger tumors, proximal tumor location, and a lower TNM stage. The recurrence rate was lower in the high-MSI group (13.7% vs. 35.4%, P = 0.006). Common patterns of distant metastasis for MUC, SRC, PDC cancers were peritoneal spread (46.9%) and hematogenous metastasis (46.4%). The 5-year CSS rates were 88.2% and 61.2% for patients with high-MSI and MSS cancers, respectively (P < 0.0001). In the multivariate analysis, except for stage-IV cancer, MSI status was an independent risk factor for cancer-specific survival (MSS: hazard ratio, 4.34; 95% confidence interval, 1.68-11.21).
  
  
  CONCLUSIONS
  In patients with colorectal cancer presenting with MUCs, SRCs, and/or PDCs, those with high-MSI cancers had better outcomes.
authors.affiliation: Department of Surgery, Yeungnam University College of Medicine, Daegu, Korea.
authors.forename: Sang Hun
authors.initials: SH
authors.lastname: Jung
authors.affiliation: Department of Surgery, Yeungnam University College of Medicine, Daegu, Korea.
authors.forename: So Hyun
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Department of Surgery, Yeungnam University College of Medicine, Daegu, Korea.
authors.forename: Jae Hwang
authors.initials: JH
authors.lastname: Kim
keywords: Colorectal neoplasms; Microsatellite instability; Mucinous cells; Poorly differentiated cells; Signet-ring cells