Not every ovarian cancer diagnosis is the same. Some types are more common and 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.

Rare Epithelial Ovarian Cancers


According to the National Cancer Institute, 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 had a chance to spread.

The prognosis for advanced mucinous carcinomas is usually worse than for advanced serous tumors, which is the more common type of ovarian cancer. Early-stage mucinous tumors have higher fiver-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, including endometriosis. They may also occur at the same time as another endometrial cancer, like cancer of the uterus.

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

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

Clear Cell

Clear cell carcinomas are the rarest of the three subtypes. Clear cell carcinoma is typically more aggressive which means the prognosis 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.

Because clear cell cancer is typically more aggressive, your doctor may suggest an equally aggressive treatment plan. Many patients with clear cell tumors undergo total hysterectomies and bilateral oophorectomies. These aggressive treatment options will prevent the cancer from moving to any nearby organs. But they will also eliminate fertility and the ability to have a child.

Treatment for Rare Subtypes of Ovarian Cancer

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

Although the treatments may be the same, the approach may be different. These subtypes tend to have a worse prognosis so your doctor may suggest a more aggressive plan.

Understanding Your Rare Subtype

Having a doctor who understands your specific type of ovarian cancer is important. You may want to see a gynecologic oncologist, or a doctor who specializes in treating cancers of the reproductive system. Knowing that you’re receiving the best care and that you’re following the best treatment plan can help you feel more comfortable.