Objective To study the genetic regulation mechanism of colorectal LST,polypoid adenomas and clolrectal cancer by detecting the expression of p53,c-myc and Ki-67 in these three lesions.Methods The expressions of p53,c-myc,Ki-67 were determined via two-step of immunohistochemistry method in LST,polypoid adenomas,invasive colorectal cancer and their significant difference were compared.Statistical analyses were used to analyze the correlation among Ki-67 expression and p53,c-myc expression in these three group lesions.Results Immunohistochemical staining was performed in 38 LST,62polypoid adenomas and 36 colorectal cancer.For p53 and c-myc,the positive rates in LST,polypoid adenomas and colorectal cancer were significantly different from each other.For Ki-67,the positive rates in LST and polypoid adenomas were significantly lower than that in colorectal cancer,but there was no statistical significant difference between LST and polypoid adenomas.The expression of Ki-67 did not correlate with p53and c-myc both in LST and polypoid adenomas.But in colorectal cancer,the expression of Ki-67 was strongly related to p53 and c-myc.Conclusion The expressions of p53,c-myc and Ki-67 were different in LST,polypoid adenomas and colorectal cancer,indicating that their genetic regulation mechanism might be different,and the genetic avenue for LST may be different from polypoid adenomas.