ABSTRACT
Purpose To investigate the expression of mismatch repair proteins MLH1,MSH2,MSH6 and PMS2 and their clinical significance in colorectal cancer.Methods Immunohistochemical analysis was used to detect MLH1,MSH2,MSH6 and PMS2 protein expression in formalin-fixed paraffin-embedded tissues from 102 colorectal cancer patients,and microsatellite instability (MSI) was tested in 20 cases.The relationship between MMR protein expression and clinical pathological features was also analyzed.Results 15 cases (14.7％) had MMR protein loss.The loss rate of MLH1,MSH2,MSH6 and PMS2 protein was 12.7％ (13/102),3.9％ (4/102),4.9％ (5/102) and 10.8％ (11/102),respectively.MLH1,MSH2,MSH6 and PMS2 protein losses were not related with gender,age,tumor size,depth of invasion and lymph node metastasis (P ＞ 0.05).MLH1 and PMS2 protein losses were related to histological differentiation (P ＜0.05).MSI was detected in 10 Lynch syndrome candidates.2 cases (2.0％)of high-frequency microsatellite instability (MSI-H) were identified,and the remaining 8 cases were MSS.However,10 cases without MMR expression abnormality all showed MSI-L/MSS.Conclusion Immunohistochemical detection of MLH1,MSH2,MSH6 and PMS2 can be used as primary screening for Lynch syndrome and its combination with MSI test can effectively increase the diagnostic rate in Lynch syndrome.
