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Ovarian cancer begins when abnormal cells in one or both ovaries start growing out of control. Because different types of cells make up the ovaries, there are also different types of ovarian cancer. Although these cancers are grouped together under the name “ovarian cancer,” each type has its own causes, outlook, and treatment approach.
Understanding which type of ovarian cancer you have is an important first step. However, your treatment plan also depends on other factors — including the stage of cancer, specific cell changes, and your overall health.
Ovarian cancers are divided into groups based on the type of cell in which the tumor started. The three main cell types in the ovary are:
Because cancer can begin in any of these cells, there are three main types of ovarian cancer:
Each type has its own subtypes.
About 90 percent of ovarian cancers start in the epithelial tissue, making this the most common type of ovarian cancer. Cancers that form in the fallopian tube (tubes that carry eggs from the ovary to the uterus) and in the peritoneum (the lining of the abdomen) also fall under this category.
The risk of epithelial ovarian cancer becomes higher with age. The median age at diagnosis is about 63 years, meaning that about half of people are diagnosed in their 60s or older.
Epithelial ovarian cancer is divided into four main categories based on what the cells look like under a microscope:
Serous carcinoma (another word for cancer in an organ) is further divided into high-grade and low-grade, based on characteristics of the cells.
High-grade serous carcinoma (HGSC) is the most common type of ovarian cancer, making up about 70 percent of all diagnoses. Risk factors include higher numbers of ovulations (when an ovary releases an egg).
HGSC doesn’t usually cause early warning signs. The disease is often not detected until later stages, often after the tumor has spread, causing symptoms like bloating, nausea, and breathing problems. Due to the frequent late-stage diagnosis, the five-year survival rate for HGSC remains below 50 percent. This means that fewer than half of people diagnosed with HGSC are still alive five years after diagnosis.
Studies have shown that many HGSC cases actually start in the fallopian tubes and then spread to the ovaries. It’s often difficult to distinguish fallopian tube cancer from ovarian cancer. Cancer may be present in the fallopian tubes for an average of 6.5 years before it moves to the ovaries, which may be one of the reasons why HGSC isn’t caught until later stages of disease.
Researchers estimate that 10 percent to 20 percent of people with epithelial ovarian cancer have specific mutations (changes) in certain genes. These gene changes are also linked to breast cancer and are part of a condition called hereditary breast and ovarian cancer (HBOC).
People with HBOC have changes in the BRCA1 or BRCA2 genes, which normally help repair damaged DNA in cells. When these genes don’t work as they should, cells are more likely to become cancerous. As a result, people with HBOC are more likely to develop certain cancers, often at younger ages than the general population.
Low-grade serous carcinoma (LGSC) tumors are rare, making up 6 percent to 8 percent of ovarian cancers. On average, this subtype of cancer is diagnosed between the ages of 45 and 57. LGSC tumors typically grow more slowly and can be resistant to chemotherapy.
Endometrioid cancer is the second most common type of epithelial ovarian cancer and is commonly diagnosed in midlife. Having a history of endometriosis — a condition where tissue similar to the lining of the uterus grows outside the uterus — can increase the risk of developing this type of cancer.
Endometrioid cancer is often found at an earlier stage, which may lead to a better prognosis (outlook) compared to some other types of epithelial ovarian cancer.
Clear cell carcinoma makes up approximately 5 percent to 11 percent of all cases of ovarian cancer. About half of people diagnosed with clear cell carcinoma have had endometriosis. It’s more common among younger women, according to the Foundation for Women’s Cancer. Clear cell carcinoma is typically caught in an earlier stage but can be less responsive to chemotherapy.
Mucinous tumors are a rare subtype of ovarian cancer but the most common type in women under 40, according to a study published in the journal Diagnostics. They’re often found when tumors are at an early stage. However, diagnosis is sometimes challenging as mucinous tumors may be hard to tell apart from tumors that have spread to the ovary from other locations in the body.
Peritoneal cancer is a rare type of cancer that comes from the cells that form the lining in the abdomen and pelvis. People who have had their ovaries removed can’t develop other types of ovarian cancer, but they can still have peritoneal cancer. This form of cancer is usually treated the same as HGSC, and people tend to experience similar symptoms.
Germ cell tumors develop from the cells in the ovary that make eggs. The majority of ovarian germ cell tumors are benign (noncancerous) and don’t require treatment. Cancerous germ cell tumors are rare and make up about 5 percent of ovarian cancer cases. According to the University of Texas MD Anderson Cancer Center, germ cell cancer tends to affect younger women, with 80 percent of cases found in people under 30. Treatment usually involves surgery and there are strategies to try to preserve fertility.
Following are the four primary subtypes of germ cell ovarian cancer.
Dysgerminomas are the most common type of cancerous germ cell tumor. They most often appear in women in their teens and 20s, according to Ovarian Cancer Research Alliance. These tumors are found at an early stage more than 75 percent of the time.
An immature teratoma is a cancerous tumor made up of three germ cell layers. This type of tumor accounts for less than 1 percent of ovarian cancer and is found most often in adolescents and young adults. Survival rates are generally good for this type of cancer, and fertility can frequently be preserved.
This type of tumor, also known as a “yolk sac tumor,” most often forms in children and teenagers. Endodermal sinus tumors are rare, making up about 2 percent to 3 percent of cancerous ovarian tumors. Surgery and chemotherapy can effectively treat this tumor more than 90 percent of the time. However, early diagnosis is key, as it can spread more rapidly than other types of tumors.
Nongestational choriocarcinoma is a rare type of germ cell ovarian cancer that can develop from germ cells in the ovaries. Chemotherapy is less effective in treating this form of cancer.
Stromal ovarian cancer accounts for about 5 percent of ovarian cancer cases. These cancers grow out of the ovary’s connective tissue or from the cells in the ovary that make the hormones estrogen and progesterone. This cancer frequently affects older women, although some types also affect girls, according to the MD Anderson Cancer Center. They typically grow slowly and don’t spread as quickly as some ovarian cancers.
Stromal ovarian tumors can be cancerous or noncancerous and include the following subtypes.
Ovarian fibromas are tumors that grow near the ovaries and are usually noncancerous. They often grow slowly and don’t cause symptoms. Fibromas often don’t need treatment, although larger ones may be surgically removed.
Thecomas are also usually noncancerous, but about 20 percent of thecomas develop into endometrial cancer. The tumors usually produce estrogen and may lead to symptoms such as abnormal vaginal bleeding.
Granulosa cell tumors are the most common type of stromal ovarian cancer. Adult granulosa cell tumors are usually diagnosed just after menopause, and juvenile granulosa cell tumors are rarer and found before puberty. These tumors also usually make estrogen. Granulosa cell tumors are often caught early and have a good prognosis.
Sertoli-Leydig cell tumors (SLCT) are rare, making up less than 0.5 percent of ovarian tumors. About 75 percent of cases are found in women under the age of 30, according to a study published in Diagnostic and Interventional Radiology.
Like granulosa cell tumors, SLCT tumors produce hormones, but they make testosterone as opposed to estrogen. This can lead to symptoms such as facial hair and a deeper voice. This type of tumor is often found in early stages and has a good prognosis.
Some types of ovarian cancer don’t fall neatly into the main categories of epithelial, germ cell, or stromal tumors. While very rare, these cancers may require different diagnostic tests or treatments.
One type is small cell carcinoma of the ovary, hypercalcemic type (SCCOHT), an extremely rare form of cancer that mainly affects young women, according to the Small Cell Ovarian Cancer Foundation.
It’s not clear what type of cell this cancer comes from. Around two-thirds of people with this cancer also have hypercalcemia (high levels of calcium in the blood). This cancer is often aggressive and grows quickly. Not much is known about how to treat SCCOHT because it is so rare, but early diagnosis and treatment for people with this type of ovarian cancer is critical.
On MyOvarianCancerTeam, people share their experiences with ovarian cancer, get advice, and find support from others who understand.
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I Was Diagnosed With Struma Ovarii, Papillary Thyroid Cancer On The Ovary.
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A MyOvarianCancerTeam Member
Interesting and helpful. I have stage 3c clear cell cancer.
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