Ovarian Cancer

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The Different Kinds of Ovarian Cancer

Dr. Oliver Dorigo Stanford University Medical Center

Once you’ve been diagnosed with ovarian cancer, your doctor will likely want to discuss the subtypes, or categories, or ovarian cancer, and where your cancers falls in that context. There are a few different subtypes of ovarian cancer, and the most common is what’s called “high grade serous.”

High grade, refers to the grading system used to categorize ovarian cancer by aggressiveness, while serous refers to other properties and behaviors inherent to the cancer cells. The grading system is not the same as the staging system, which categorizes how far the cancer has spread, not the degree of the cancer’s aggressiveness. In addition to high grade serous, there are several others to which women are susceptible as well.

“High grade serous is the most common type of ovarian cancer. This is a diagnosis that is made under the microscope by our pathologists,” says Dr. Oliver Dorigo, gynecologic oncologist at Stanford Medicine. 70 percent of ovarian cancer cases are determined to be high grade serous.

Ovarian cancer subtypes are classified by the type of cells and tissue out of which they originate. The subtypes include: epithelial ovarian cancer, stroma cell ovarian cancer and germ cell ovarian cancer, according to Dorigo. Age is a major factor that impacts a woman’s susceptibility to certain kinds of ovarian cancers.

Around 90 percent of ovarian tumors develop from epithelial cells which are in the surface layer of cells covering the ovary. These tumors generally occur in women over the age of 50. Most epithelial tumors are actually benign meaning that they are not harmful and are noncancerous, but they can be cancerous as well. Epithelial ovarian cancers include high grade serious, low grade serious, endometrioid, mucinous, brenner tumors, borderline tumors, clear cell, unclassified and ovarian carcinosarcoma.

Only five percent of cases come from stromal cells, which are the cells that make up the core of the ovary. These tumors can occur at any age, though some occur more commonly during adolescence.

The remaining five percent of ovarian cancer tumors originate in germ cells, which are the cells that eventually mature into eggs. These kinds of tumors happen primarily in younger women. Usually, germ cell cancers only occur in on ovary. In addition, there are also rarer kinds of ovarian cancer that emerge within the connective tissue, such as sarcoma.

“Most ovarian cancer patients have high grade serous disease, it is approximately 85 percent. These are typically very aggressive cancer cells that are quickly dividing but in return it is also very sensitive to chemotherapy, thus the patient responds better to chemotherapy and traditional surgery,” explains Dr. Emese Zsiros, gynecologic oncologist at Roswell Park Comprehensive Cancer Center in Buffalo, New York.

There are some women, though, a small subset of patients, who have low grade ovarian cancer. Low grade ovarian cancers tend to grow more slowly over time as opposed to dividing quickly like high grade serous does. The low grade ovarian cancer resembles normal ovarian tissue. And as a result of low grade ovarian cancer’s qualities, it is not as responsive to normal chemotherapy as high grade serous does.

Because low grade patients do not respond as well to chemotherapy, those women often require further surgery, according to Zsiros. These further surgeries are used to remove any residual disease or any recurrence of the cancer.

It is important to note that some cancers are now being typified as fallopian tube or primary peritoneal cancer instead of being called ovarian cancer, according to Target Ovarian Cancer, but are still being treated in the same manner in which ovarian cancer is treated. The women diagnosed with fallopian tube or primary peritoneal cancer are eligible for the same clinical trials as patients fighting ovarian cancer.

Once it is identified the kind of tumor the woman has and diagnosed that they have ovarian cancer, a doctor determines what stage of cancer that the woman is facing. To make this determination, a doctor generally has to perform surgery.

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Dr. Oliver Dorigo is a gynecologic oncologist at Stanford University Medical Center. Read More