CA-125 !

CA-125 is a mucin of coelomic linings; it follows epithelial ovarian cancer but rises in many benign conditions.

Updated 2026-11-01

Key facts

A mucin-type glycoprotein (MUC16) of coelom-derived linings: peritoneum, pleura, pericardium, endometrium, fallopian tubes.
Main use: follow-up of epithelial (serous) ovarian cancer during and after treatment.
It is not useful to screen women without high risk: it is normal in many early-stage cancers.
It rises in endometriosis, menstruation, pregnancy, pelvic inflammatory disease, fibroids, cirrhosis with ascites, pleural effusion and heart failure.
It is more useful after menopause, when there are fewer benign causes; its reference value varies by laboratory.

What it measures: CA-125 antigen in serum by immunoassay.
Where it comes from: mesothelial and Müllerian cells express it on their surface; any serosal irritation or epithelial tumour releases it.
Why it rises: epithelial ovarian cancer, other cancers (endometrium, tube, pancreas, lung), peritoneal or pleural irritation of any cause.
Pitfalls: false positives are common before menopause; any ascites raises it.
It is combined with ultrasound and menopausal status in risk-of-malignancy indices to decide referral of an adnexal mass.

A complex adnexal mass with a high CA-125 in a postmenopausal woman is referred to gynaecological oncology.
A CA-125 rising again after chemotherapy may herald relapse before symptoms.
In women with BRCA mutations it has been used with ultrasound for surveillance, with limited benefit.

Think of the answer, then tap the question to see it.

Which cancer is followed with CA-125?

Epithelial ovarian cancer, especially the serous type.

Why is CA-125 more useful after menopause?

Before menopause many benign causes raise it (endometriosis, menstruation, fibroids, pregnancy).

What do the benign causes of a high CA-125 have in common?

They irritate coelomic linings (peritoneum, pleura, pericardium) or the endometrium, which express this mucin.

Is CA-125 useful to screen for ovarian cancer in women without high risk?

No; it is normal in many early tumours and gives frequent false positives.

Educational information, not medical advice. For any symptom, see a health professional.

Sources: CA-125 Blood Test (Ovarian Cancer): MedlinePlus Medical Test (MedlinePlus, US National Library of Medicine, 2026); CA-125 blood test: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake

Representative model, for educational purposes only.