Immunohistochemical analysis of CA125, CA19-9, and Ki-67 in stage III or IV endometriosis: positive correlation between serum CA125 level and endometriotic epithelial cell proliferation

Background Serum levels of CA125 and CA19-9 are often elevated in patients with endometriosis, but the clinical or biological significance of this is not well established. The aim of the present study was to compare serum and tissue levels of CA125 and CA19-9, and to examine the correlation between these levels and cell proliferation using immunohistochemical analysis in stage III or IV endometriosis. Methods. Forty-five cases diagnosed histologically as endometriosis were analyzed (26 cases were stage III and 19 were stage IV using the revised American Fertility Society classification). The preoperative serum levels of CA125 and CA19-9 were measured by immunoradiometric assay. Immunohistochemical analysis was performed using antibodies against CA125, CA19-9, and Ki-67 (a representative marker of cell proliferation). Results. The serum levels of CA125 and CA19-9 were elevated (over the cutoff values) in 25 cases and 21 cases, respectively. There was no significant correlation between serum CA125 and serum CA19-9 levels (correlation coefficient [rho]=0.19). The serum CA19-9 level correlated well with the degree of immunostaining for CA19-9 (rho=0.57), but not with the Ki-67 labeling index. The serum CA125 level did not show a strong correlation with CA125 staining (rho=0.41), but it correlated well with the Ki-67 labeling index (rho=0.53). Conclusions. The present study indicates that the serum CA125 level may correlate with the proliferative activity of epithelial cells in endometriotic lesions.