Cancer antigen 125 is a tumor marker associated with:

• A. Breast cancer
• B. Colon cancer
• C. Lung cancer
• D. Ovarian and endometrial carcinoma

Answer: (D)

CA-125 is a tumor marker most closely linked to ovarian epithelial cancers. It’s a high‑molecular‑weight glycoprotein produced by cells arising from the coelomic epithelium, including the ovarian surface epithelium. In clinical practice, elevated CA-125 levels help monitor how well treatment is working and guide surveillance for recurrence in ovarian cancer, especially when imaging supports the finding. It’s not specific to cancer, though—levels can rise with benign conditions such as menstruation, endometriosis, pelvic inflammatory disease, liver disease, and pregnancy. CA-125 can also be elevated in endometrial cancer, particularly in more advanced cases, which is why this marker is associated with both ovarian and endometrial carcinoma. It is not routinely used as a screening tool for the other cancers listed, where different markers or tests are preferred.