This study aims to analyze sensitivities and polymorphisms of the Bethesda panel markers (BAT25, BAT26, D2S123, D5S346 and D17S250) for microsatellite instability testing in Chinese from Jiangsu Province and their clinical implication.

MSI, sensitivity and polymorphism analysis in 541 colorectal cancer (CRC) patients were detected by fragment analysis.

Five hundred and twenty-five tissue samples and 541 blood samples of the 541 sample pairs were successfully amplified. Thirty-four (6.5%) cases were MSI-high (MSI-H) while 33 (6.3%) and 458 (87.2%) were MSI-low (MSI-L) and microsatellite stable (MSS), respectively. BAT26 (85.3%) exhibited the highest instability followed by BAT25 (82.4%), D2S123 (67.6%), D17S250 (64.7%) and D5S346 (50.0%) in MSI-H cases. The median ages of CRC patients with LS, MSI-H, MSI-L and MSS status were 38–43, 48, 60 and 63, respectively. 75.0%, 44.1%, 12.1% and 7.0% CRC cases were mucinous carcinomas in LS, MSI-H, MSI-L and MSS group, respectively. For D2S123, D17S250 and D5S346, heterozygosity was 80.8%, 74.1% and 57.7% and sizes of polymorphic variation range (PVR) were 207bp to 234bp, 140bp to 169bp and 109bp to 137bp, respectively. For D2S123 and D5S346, there was a bimodal distribution distinguishing the D17S250 from an indistinct trimodal or tetramodal distribution.

MSI-H cases showed earlier onset and higher proportion of mucinous carcinomas. Mononucleotide BAT26 and BAT25 exhibited higher sensitivity than dinucleotides D2S123, D17S250 and D5S346 in the Chinese population. The dinucleotide markers were highly polymorphic with high percent of heterozygosity, great variation in repeat length and non-normal distribution in Chinese population from Jiangsu Province.