It is estimated that ovarian cancer was the fifth most diagnosed female cancer in 2010, as nearly 22,000 women were diagnosed with the disease (which represents around 5 percent of all female cancers).

There are three different types of malignant tumors that ovarian cancer can originate from:

• Epithelial tumors
• Germ cell tumors
• Stromal tumors

It is important to note that some ovarian tumors are benign and stay confined to the ovary. Some women with these types of tumors will decide to act preemptively and have either part of the ovary or the entire ovary removed to eliminate the chance that the tumors eventually become malignant.

Epithelial tumors

This form of malignant tumor begins in the cells that line the surface of the ovary, and it accounts for the majority of ovarian cancer diagnoses. Epithelial tumors can be benign, but there are two sub-types it can classified as which are cancerous – tumors of low malignant potential and those which are malignant.

Tumors of low malignant potential are less life threatening than malignant epithelial ovarian tumors. Although they affect younger women more often than other ovarian cancers, they develop very slowly. Malignant epithelial ovarian tumors are deadly, however. This type of tumor accounts for 90 percent of all ovarian cancers. Grades of severity ranging from 1 to 3 are given for this type of tumor, and a grade of 3 means the tumor is significantly advanced.

Germ cell tumors

This form of ovarian tumor arises from the cells that produce a woman’s eggs. Most of these tumors are non-cancerous, but they have the potential to be malignant. In comparison to malignant epithelial tumors, a typical prognosis for ovarian cancer caused by germ cell tumors is good. Nine out of ten women with this form of ovarian cancer survive at least five years. Some of the sub-classifications for germ cell tumors are known as teratoma, dysgerminoma, endodermal sinus tumors, and choriocarcinoma.

Stromal tumors

This form of ovarian cancer is rare. These tumors can be either benign or malignant, and often develop from cells that produce hormones. Types of malignant stromal tumors are granulosa cell tumors, granusola-theca tumors and Sertoli-Leydig cell tumors. Women diagnosed with this form of ovarian cancer have a 70 percent 5-year relative survival rate.

There are other forms of ovarian cancers, but they are extremely rare. Primary peritoneal carcinoma begins in the cells lining the pelvis and abdomen, but is still classified as an ovarian cancer. Women who have had their ovaries surgically removed are still susceptible to this form of cancer. Fallopian tube cancer is another rare form of cancer, but it causes many of the same symptoms as ovarian cancer. Survival rates for this disease are relatively higher than in women with ovarian cancers.