There are different types of ovarian cancer. Some are more common or less serious than others. Around 85 to 90 percent of ovarian cancers are epithelial ovarian tumors. Ovarian tumors can also be from three other, rarer subtypes: mucinous, endometrioid, and clear cell.

According to one study, less than 5 percent of ovarian cancers diagnosed each year in the United States are mucinous tumors.

Mucinous tumors tend to be found earlier than other types of epithelial cancers. This means that treatment can begin before the tumor has spread.

The outlook for advanced mucinous carcinomas is usually worse than for advanced serous tumors. Serous is a more common type of ovarian cancer.

Early-stage mucinous tumors have higher five-year survival rates than late-stage tumors.

About 2 to 4 percent of ovarian tumors are endometrioid tumors. Endometrioid carcinomas are often the result of a disease in the reproductive system, such as endometriosis. These tumors can occur at the same time as another endometrial cancer, like cancer of the uterus.

Endometrioid tumors are most common in women ages 50 to 70. Women with a family or personal history of colon or endometrial cancer have a higher risk. Women with endometriosis are also at higher risk for developing this rare type of cancer.

The five-year survival rate for women with cancerous endometrioid tumors is 83 percent. Treatment is typically more successful the earlier the cancer is found.

Clear cell carcinomas are the rarest of the three subtypes. Clear cell carcinoma is typically more aggressive. This means the outlook is often worse.

Like endometrioid carcinomas, clear cell tumors can be caused by endometriosis or noncancerous tumors. This subtype is also more common among women of Japanese ancestry.

Clear cell cancer is typically more aggressive than other types. So your doctor may suggest an equally aggressive treatment plan.

Many women with clear cell tumors undergo total hysterectomies and bilateral oophorectomies. These aggressive treatments prevent the cancer from moving to nearby organs. They also cause infertility.

These rare subtypes may be unique among the other ovarian cancers. But most women with one of these subtypes will get the same treatment as women with a more common type of ovarian cancer.

The treatments may be the same, but the approach could be different. These rare subtypes tend to have a worse outlook, which means your doctor may suggest a more aggressive plan.

It’s important to see a doctor who understands your type of ovarian cancer. You may want to see a gynecologic oncologist, or a doctor who specializes in treating cancers of the reproductive system. When you know you’re getting the best care, it may help you feel more comfortable.