Ovarian cancer is so named because it arises from the ovary. But there are a lot of different types of cells in the ovaries, and each of these cell types can become cancerous. These cells all have different functions and produce different biochemical substances.
These substances can be measured in the blood stream and are called tumor markers.
Why Your Doctor Runs Tumor Marker Blood Tests
In some cases, the marker is a substance that is produced exclusively by abnormal cells. However, in most cases, these markers are simply produced in abnormally high levels as the cancerous cells rev up various parts of their biochemical machinery.In either case, this means that your doctor can check your blood to test for tumor markers, indicating what type of cancer is present, or later on, how well your treatment is working. Generally, tumor markers decrease whenever treatment is effective. The most common cancer of the ovary is called epithelial ovarian cancer. There are three subtypes: mucinous, serous and endometrioid. The next most common groups are called germ cell and sex-cord stromal cancers. Each of these has a number of subtypes, but the markers are the same for each of these larger groupings.
Epithelial Ovarian Cancer and the CA-125 Test
A marker known as "CA-125" is the most common marker used for this group of cancers. However, mucinous ovarian cancers are less likely to produce CA-125 than serous or endometrioid subtypes. Other tumor markers that can be useful for monitoring mucinous ovarian cancers are CA-72-4, CA-19-9 and CEA (carcinoembryonic antigen). There are others which may be elevated, but are far less commonly used.
Germ-Cell Tumors
The two main markers used for this group of cancers are: alpha-feto protein (AFP) and human chorionic gonadotropin (hCG). The latter is also used to monitor normal pregnancy.
Sex-cord Stromal Tumors
The only markers in this category that are useful are produced by the granulosa cell subtype. Specifically, they are estradiol (a type of estrogen) and inhibin.
Source: Berek, Johanthan S. "Practical Gynecological Oncology." Lippincott Williams & Wilkins, 2004
