[A study on microsatellite instability status for colorectal serrated lesions]

To verify the traditional serrated pathway by comparing microsatellite instability (MSI) status among traditional serrated adenoma, traditional adenoma, serrated colorectal cancer and non-serrated colorectal cancer.Seventy-five paraffin-embedded tissue samples, including 15 with serrated adenocarcinoma (Sca), 20 with non-serrated adenocarcinoma (N-Sca), 20 with traditional serrated adenoma (TSA) and 20 with villous adenoma (AD) were collected from the pathology department of our hospital. Genomic DNA was extracted from these samples and then amplified with fluorescently-labeled primer specific for BAT25 and BAT26. The MSI status was detected with DNA automatic sequencer.Six of 18 samples with TSA harbored MSI-H and twelve MSI-L/MSS; 18 samples with conventional adenoma were exclusively of MSS; 3 of 13 samples of serrated carcinoma harbored MSI-H and ten MSI-L/MSS; 18 of 19 N-Sca samples harbored MSI-L/MSS and only one MSI-H. With Chi-square test, the MSI frequency in AD group and N-Sca group was significantly lower than that in TSA group and Sca group (P0.05); but with no statistical difference between the TSA group and Sca groups (P0.05).MSI-H frequency in AD group and N-Sca group was obviously lower than that of TSA group and Sca group. It is concluded that there might be a new traditional serrated neoplasia pathway which is different from the conventional adenoma-carcinoma carcinogenesis pathway, but we still need prospective follow-up studies to verify its existence.