Ovarian Cancer Tumor Markers

Epithelial Ovarian Cancer, Germ Cell, and Sex-Cord Stromal Tumor Markers

Young woman scientist viewing blood tube during clinical testing of medical samples in a laboratory
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As an ovarian cancer patient, you've probably run across the term "tumor markers." But what does that mean?

Ovarian cancer is so named because it arises from the ovary (or the fallopian tubes next to 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 bloodstream and are called tumor markers.

Why Your Doctor Runs Tumor Marker Blood Tests

In some cases, the tumor 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.  Doctors refer to tumors that produce greater amounts of these substances as tumors that express these markers. For example, instead of saying that ovarian cancer produces abnormally high amounts of CA-125, they may say that the cancer expresses CA-125.

Types of Ovarian Cancers

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 more rare types of ovarian cancers 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 Tumor Markers

The CA-125 tumor marker blood test is the most common marker used for this group of cancers. CA stands for "cancer antigen."  CA-125 can be made by normal cells  but is made in higher concentration in some ovarian cancer cells than normal ovarian cells.

CA-125 may be used as part of an ovarian risk index to diagnose ovarian cancer, or it may be used to monitor the response to ovarian cancer treatments.  Not all ovarian cancers express CA-125, and levels are normal in around 20% of these type of ovarian cancers.  In contrast, some benign ovarian tumors, as well as other conditions, may result in an elevated CA-125 level.

Of the 3 subtypes of epithelial ovarian cancer, mucinous cancers are less likely to express CA-125 than either serous or endometrioid tumors.

HE4 - human epididymis protein 4 is a newer tumor marker that may also be expressed in ovarian cancer, and like CA-125 is more likely to be found with serous and endometrioid tumors.  Some researchers have found that using a combination of CA-125 and HE4 is more helpful in diagnosing ovarian cancer than either test used alone.

Since women under the age of 40 are more likely to have the mucinous subtype of epithelial ovarian cancer, these 2 tumor markers may be less helpful in the diagnostic process for younger women.

Other tumor markers that can sometimes 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.  CA 19-9 is commonly found in women with the mucinous subtype and may be helpful in the diagnostic process when combined with CA-125.

Germ-Cell Tumor Markers

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.  Levels of AFP and hCG which are significantly elevated are a highly specific way in diagnosing these tumors.

Sex-cord Stromal Tumor Markers

The only markers in this category that are useful are produced by the granulosa cell subtype.  These include estradiol (a type of estrogen) and inhibin.  Since these tumors are often found in young women, these tests may be done as part of a workup for an abdominal mass (and other symptoms such as precocious puberty) in girls and young women.


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