Indicator Explainer
CA-125 Antigen
An antigen expressed by tissues derived from mullerian epithelium (tubal, endometrial and endocervical) or celomic epithelium (mesothelial cells of the pleura, pericardium and peritoneum). Although its biochemical nature has not been clearly defined, CA125 has been described as a glycosylated, high-molecular-weight protein that may be released from damaged cells. Measurable in plasma, CA125 is a sensitive, nonspecific tumor marker for ovarian cancer; as such it is much more useful for monitoring clinical responses to the treatment of ovarian cancer than for the diagnosis of ovarian cancer. Elevated plasma CA125 may occur in association with other malignancies and non-malignant gynecologic disorders. (NCI04)
This page explains what the indicator is and how results are interpreted in general terms. Reference ranges depend on the laboratory, the method, and your own situation — no single “normal value” applies to everyone. This page is health information, not a diagnosis. For symptoms, treatment, or urgent concerns, contact a healthcare professional.
When it is tested
Source: National Cancer Institute, NCI Thesaurus 26.09d, C325. NCI definition, reproduced without modification under CC BY 4.0. Source identity and definition checked automatically on 2026-10-18. No individual clinical interpretation or human reviewer is asserted.
Reading results
Reference intervals and interpretation depend on the laboratory, specimen, method and clinical context. This source definition is educational information; it does not establish a diagnosis, product approval or suitability for an individual.