Malignant lesions of the ovaries include primary lesions arising from normal structures within the ovary and secondary lesions from cancers arising elsewhere in the body. Primary lesions include epithelial ovarian carcinoma (70% of all ovarian malignancies), germ-cell tumors, sex-cord stromal tumors, and other more rare types. Metastases to the ovaries are relatively frequent, with the most common being from the endometrium, breast, colon, stomach, and cervix.

Although many histologic types of ovarian tumors have been described, more than 90% of ovarian malignancies are epithelial tumors. Many of these actually originate in the fallopian tubes.

The precise cause of ovarian cancer is unknown. However, several risk and contributing factors (including both reproductive and genetic factors) have been identified.

Ovarian cancer is the most common cause of cancer death from gynecologic tumors in the advanced countries. Around the world, more than 200,000 women are estimated to develop ovarian cancer every year and about 100,000 die from the disease. The lifetime risk of a woman developing epithelial ovarian cancer is 1 in 70.