While the causes of ovarian cancer are still unknown, scientists have some theories:

• Genetic errors may occur during one’s life known as acquired (somatic) gene mutations;
• A person can be born with gene mutations (hereditary gene mutations also known as germline mutations);
• Because being pregnant and taking birth control pills can lower risk of ovarian cancer, ovarian cancer may be related to ovulation;
• Though thought of as male hormones, androgens are found in women at lower levels and may play a role in ovarian cancer;

Additionally, based on research, it is believed that many if not almost all high-grade serous ovarian cancers (the most common subtype) previously thought to originate in the ovaries actually arise from precursor lesions that begin in the fallopian tubes.

Primary peritoneal carcinoma is thought to develop from cells in the lining of the abdomen and pelvis, called the peritoneum.  These cells are very similar to cells on the surface of the ovaries—some researchers believe primary peritoneal carcinoma may also begin in the cells lining the fallopian tubes.

Other subtypes diagnosed as primary peritoneal carcinoma share molecular similarities, as well, and therefore high-grade serous carcinomas that originate from the fallopian tube and elsewhere in the peritoneal cavity, together with most epithelial cancers, are staged and treated similarly.

Since 2000, fallopian tube cancer and primary peritoneal cancer have generally been included in ovarian cancer clinical trials. Regardless of the site of origin, the hallmark of these cancers is their early peritoneal spread or metastases.