Tumor microsatellite instability and clinicopathologic features in Iranian colorectal cancer patients at risk for Lynch syndrome

Abstract

Background: Microsatellite instability (MSI) is a mutational signature that is the hallmark of Lynch syndrome, and MSI testing is a cost-effective method to screen the disease. Since there is no enough data about MSI status and associated clinicopathologic features of hereditary nonpolyposis colorectal cancer (HNPCC) in Iran, our study is a new trial to describe them in center of Iran (Isfahan). Materials and Methods: It is a descriptive retrospective study to screen HNPCC families using Amsterdam II criteria in Central Iran within 2000-2013. For MSI testing, we used a commercially available kit evaluating mononucleotide markers (BAT-25, BAT-26, MON0-27, NR-21 and NR-24). After a fluorescent multiplex polymerase chain reaction amplification of the markers,samples were sequenced to fragment analysis. Data analysis was performed using SPSS 16 software (SPSS Inc., Chicago, IL, USA).Results: Overall, 31 of 45 screened HNPCC families were eventually included to MSI testing. Totally, 9/31 patients (29.0%) showed MSI in their tumor tissues. BAT-26 was the most instable marker with instability in 7/24 MSI tumors (29.2%). The mean age at diagnosis in microsatellite stable (MSS), MSI-Low (MSI-L), and MSI-High (MSI-H) probands was respectively 44.7 (standard deviation [SD]= 11.83), 51.7 (SD = 16.17), and 36.0 (SD = 3.41) years. The most common tumor sites in MSS, MSI-L, and MSI-H probands were rectosigmoid (~72.8%), rectum (66.7%) and right colon (50.0%), respectively. Of 186 cancer patients among 31 HNPCC families,86 patients (46.2%) had colorectal cancer (CRC) and 100 patients (53.8%) had extracolonic cancers. The average of CRC affected members among MSS, MSI-L, and MSI-H groups of our HNPCC families was 2.2 (SD = 1.30), 3.3 (SD = 3.21), and 4.7 (SD = 2.42)patients per family, respectively. Stomach with 18.3% and 26.7% of all extracolonic cancers were most common involved organ in MSS and MSI-H families, respectively. Conclusion: Our different molecular results could be suggested to describe HNPCC families based on some new molecular mechanisms leading to MSS HNPCC phenotypes. Meanwhile, more evaluations within our population are recommended.

Key words: Clinicopathologic, Iran, Lynch syndrome, microsatellite instability