Abstract: Objective:To study the association of the expression of Ki-67,E-Cad and nm23 with the volume,hormone secretion and invasion of pituitary adenomas.Methods:The expression of Ki-67,E-Cad and nm23 in 52 cases of pituitary adenomas was examined by immunohistochemical methods.Results:The expression level of Ki-67 in the invasive and nonsecretive pituitary adenomas was significantly higher than that in the noninvasive and secretive ones,and the expression level of Ki-67 was not related to the volumes of pituitary adenomas (P>0.05).The expression level of E-Cad in the invasive and unsecretive pituitary adenomas was significantly lower than that in the noninvasive and secretive ones (P<0.05),and the expression level of E-Cad was negatively correlated with the volumes of pituitary adenomas (P>0.05).The expression level of nm23 in the invasive pituitary adenomas was significantly lower than that in the noninvasive ones (P<0.05),and was not related to the hormone typing and volume of the tumor (P>0.05).Conclusions:High expression of Ki-67 and low expression of E-cad and nm23 are positively related to the invasiveness of pituitary adenomas,and may affect the cell differentiation and promote proliferation of the cells in pituitary adenomas.Thus,the expression of Ki-67,E-Cad and nm23 could be used to evaluate the invasion and prognosis of pituitary adenoma.