Not all ovarian cancer is the same. There are many different types of ovarian cancers, depending on the kind of tumor a person has. Each type spreads differently, and treatments and prognosis (predicted course of the disease) are also different for each.
The ovaries are made up of 3 main types of cells. Each cell type can develop into a different kind of tumor. The types include:1
- Epithelial tumors
- Germ cell tumors
- Stromal tumors
Some tumors are not cancerous (benign) and stay within the ovary. Tumors that are cancerous or borderline cancerous can spread to other areas of the body.1,2
Epithelial ovarian tumors
Epithelial ovarian tumors develop from epithelial cells. These are cells that are on the outer surface of the ovaries. Most of these tumors are not cancerous. However, cancerous epithelial tumors are the most common kind of ovarian cancer. These make up 85 to 90 percent of ovarian cancers.1,2
There are different types of cancerous epithelial ovarian tumors. They are classified based on the results of a pathology report. This is a microscopic exam of a biopsy sample or tumor that has been surgically removed. Cancerous epithelial ovarian tumors can include:1
- Serous carcinomas
- Clear cell carcinoma
- Mucinous carcinoma
- Endometrioid carcinoma
Serous carcinomas are by far the most common type of cancerous epithelial ovarian tumors.1,2
Some epithelial ovarian tumors are borderline tumors. This means that under a microscope they do not clearly look cancerous. These are called borderline epithelial ovarian carcinomas. They are unlike typical ovarian cancers because they do not grow into the supporting ovarian tissues.1,2
If these borderline tumors do spread, they can grow on the lining of other areas, such as the abdomen, but not into it. These borderline tumors usually affect younger women and grow more slowly than other ovarian cancers.1,2
Fallopian tube cancer (FTC) and primary peritoneal carcinoma (PPC) are other types of cancer that are often grouped together with epithelial ovarian cancer. FTC and PPC are rare cancers, but their symptoms, disease spread, and treatment are similar to ovarian cancer.2
Germ cell tumors
Germ cells usually form the eggs in women and sperm in men. Ovarian germ cell tumors grow from these cells. Most ovarian germ cell tumors are not cancerous. Fewer than 2 percent of ovarian cancers are germ cells tumors.1
There are several different subtypes of ovarian germ cell tumors. They are classified based on the results of a pathology report. In some cases, germ cell tumors can be a mix of subtypes. The most common subtypes include:1,2
- Teratomas
- Dysgerminomas
- Endodermal sinus tumors (yolk sac tumors)
- Choriocarcinomas
Cancerous germ cell tumors generally occur in teenage girls and women in their 20s.2
Stromal tumors
Ovarian stromal tumors develop from the connective tissue cells that hold the ovary together. These cells also produce the hormones estrogen and progesterone. Ovarian stromal cell tumors are rare, making up only about 1 percent of ovarian cancers.1,2
Stromal tumors may be cancerous (malignant) or noncancerous (benign). Malignant stromal tumors are classified into 3 subtypes:1
- Granulosa cell tumors
- Granulosa-theca tumors
- Sertoli-Leydig cell tumors
All types of stromal tumors are usually found at early stages and often have good outcomes.2