CA125 and ovarian cancer

CA125 (cancer antigen 125 or carbohydrate antigen 125 also known as mucin 16) is best known as a blood-borne biomarker for ovarian cancer. However, CA125 may also be elevated in other cancers, including those originating in the endometrium, fallopian tubes, lungs, breast and gastrointestinal tract. CA-125 can also become elevated with endometriosis, several diseases of the ovary, and pregnancy.

CA-125 is not perfectly specific or perfectly sensitive for ovarian cancer since not every patient with this form of cancer will have an elevated level in the blood. In fact, 79% of all ovarian cancers are positive for CA-125, while the remainder do not express the antigen.