Immunohistochemical expression of CA 125 in endometrial adenocarcinoma: correlation of antigen expression with metastatic potential.

Immunohistochemical localization of CA 125 using murine monoclonal antibody OC 125 was performed on fresh frozen tissue from 44 endometrial adenocarcinomas and 26 benign endometria. Immunohistochemical evaluation incorporated both intensity and distribution of staining (CA 125 HSCORE). Thirty-seven cancers (84%) and 23 benign endometria (88%) expressed immunohistochemically detectable CA 125. Staining was confined to epithelial cells and was present both on the cell membrane and in the cytoplasm. Among the 44 endometrial cancers, CA 125 HSCORE did not correlate with histological grade, depth of myometrial invasion or estrogen/progesterone receptor levels. Following surgical staging, 13 patients (30%) were found to have extrauterine metastatic disease. The median CA 125 HSCORE of patients with metastatic disease (2.25) was significantly higher than that of patients with disease confined to the uterus (0.6) (P less than 0.001). In addition, high CA 125 HSCORE also correlated with the presence of lymph node metastasis (P less than 0.001). The results of this study suggest that high CA 125 expression by endometrial adenocarcinomas is associated with increased metastatic potential.