Many types of tumors can start in the ovaries. Some are benign (not cancer) and never spread beyond the ovary. Women with these types of tumors can be treated by taking out either the ovary or the part of the ovary that has the tumor. Other types of tumors are cancerous (or malignant) and can spread to other parts of the body. They need more treatment which we will explain later.
As a rule, tumors in the ovary are named for the kinds of cells the tumor started from and whether the tumor is benign or cancerous. There are 3 main types of tumors:
Epithelial tumors: These tumors start from the cells that cover the outer surface of the ovary. Most ovarian tumors are epithelial cell tumors.
Germ cell tumors: These start from the cells that produce the eggs.
Stromal tumors: These start from cells that hold the ovary together and make the female hormones.
Each of these types of tumors is explained in more detail below.
Epithelial ovarian tumors
Epithelial ovarian tumors are further divided into 3 sub-groups:
Benign epithelial tumors: These tumors are not cancer. They do not spread and usually do not lead to serious illness.
Tumors of low malignant potential (LMP tumors): These tumors do not clearly appear to be cancer when looked at under the microscope. They are also known as borderline tumors. They tend to affect women at a younger age than other ovarian cancers. They grow and spread slowly and are less life-threatening than most ovarian cancers.
Epithelial ovarian tumors: Nearly 9 out of 10 ovarian cancers are this type. When someone says they have ovarian cancer, they usually mean this type. Cancer cells of this type have certain features that can be seen under a microscope. These features allow doctors to further classify them. These tumors are also given a grade depending on how much the cells look like normal cells. Grade 1 means the cells look more normal; grade 3 look less normal, and grade 2 is in between. Usually the higher the grade the worse the outlook.
Primary peritoneal carcinoma
This is a rare cancer much like epithelial ovarian cancer but it starts outside of the ovaries. It grows from the cells that line the pelvis and belly (abdomen). These cells look a lot like the cells on the surface of the ovaries. Women who have had their ovaries removed can still get this type of cancer. Symptoms of this cancer are much like those of ovarian cancer. Treatment is also much the same.
Fallopian tube cancer
This is a very rare cancer. It begins in the tube that carries an egg from the ovary to the uterus (called the fallopian tube). Fallopian tube cancer causes symptoms much like those seen in women with ovarian cancer. The treatment and outlook for survival (prognosis) is slightly better than that for ovarian cancer.
Germ cell tumors
Germ cells are the cells that usually form the eggs (ova). Most germ cell tumors are not cancer, but some can be. Germ cell tumors are rare. As a rule, they have a good outlook, with more than 9 out of 10 patients surviving at least 5 years after the tumor is found. There are subtypes of germ cell tumors. The most common are teratoma, dysgerminoma, endodermal sinus tumor, and choriocarcinoma. Germ cell tumors can also be a mix of more than one subtype.
Stromal tumors can be either benign (not cancer) or cancer. More than half are found in women over age 50, but they can also be found in young girls. Many of these tumors make hormones. There are many different types of stromal tumors. Types of malignant (cancerous) stromal tumors include granulosa cell tumors, granulosa-theca tumors, and Sertoli-Leydig cell tumors, which are thought to be low-grade cancers. Thecomas and fibromas are benign stromal tumors. These tumors have a good outlook, with almost 9 out of 10 patients living at least 5 years after the tumor is found.
An ovarian cyst is fluid that collects inside an ovary. Many of these cysts are harmless. The fluid will most often be absorbed and the cyst will go away in time without any treatment. But if the cyst is large, does not go away on its own in a few months, or happens in childhood or after menopause, the doctor may want to do more tests. This is because a very small number of these cysts can be cancer.