What is Ovarian Cancer?

This is the first article in the Understanding Ovarian Cancer Guide. This guide was developed by the HealthTree Education Team and was last updated and reviewed on May 20, 2026

Cancer begins when cells in the body start to grow out of control. Ovarian cancer starts in the cells of the ovaries, fallopian tubes, or peritoneum (the lining of the abdomen). Many cancers historically called “ovarian” are now thought to begin in the fallopian tubes.

When you have ovarian cancer, cells in these tissues do not follow the normal cell cycle. Healthy cells grow, copy themselves, and then die. Cancer cells change, grow faster than normal, and do not die the way they should.

What are the ovaries?

The ovaries are two small, almond-shaped organs located on either side of the uterus in the pelvis. They are part of the female reproductive system and have two main jobs:

• Producing eggs for reproduction
• Producing the hormones estrogen and progesterone

The ovaries are connected to the uterus by the fallopian tubes, which carry eggs from the ovaries to the uterus. Cancer can begin in any of the cells that make up the ovaries and fallopian tubes:

• Epithelial cells line the outer surface of the ovary and the fallopian tubes. Most ovarian cancers begin in these cells.
• Germ cells produce the eggs.
• Stromal cells form the structural tissue of the ovary and produce hormones.

How ovarian cancer starts

Most ovarian cancers develop when changes build up in the DNA of cells in the fallopian tubes or ovaries. Mutations, such as BRCA1 or BRCA2, can be inherited from a parent or acquired during a person's lifetime. Over time, these damaged cells can grow out of control. Research now suggests that many “ovarian” high-grade serous cancers actually begin in the fallopian tubes and later spread to the surface of the ovary.

How does ovarian cancer affect the body?

As ovarian cancer grows, it can affect many parts of the body:

How ovarian cancer affects the pelvis and abdomen:

Ovarian cancer often spreads first within the abdomen. Tumors can grow on the surface of the ovaries, fallopian tubes, uterus, bladder, intestines, and the lining of the abdomen, called the peritoneum. This can cause bloating, abdominal swelling, pain, and changes in bowel or urinary habits.

How ovarian cancer affects the lymph nodes:

Ovarian cancer can spread to lymph nodes in the pelvis and around the major blood vessels in the abdomen.

How ovarian cancer affects other organs:

When cancer spreads to other parts of the body, it has metastasized. Ovarian cancer most commonly spreads within the abdomen, but it can also spread through the bloodstream to the liver, lungs, or, less commonly, the brain or bones. This can affect how these organs function and may cause additional symptoms.

Learn more about the signs and symptoms of ovarian cancer.

Types of ovarian cancer

There are several types of ovarian cancer, classified by the type of cell where the cancer begins:

• High-grade serous carcinoma (HGSC). The most common subtype, accounting for the majority of epithelial ovarian cancers. Often diagnosed at an advanced stage and frequently associated with BRCA1 and BRCA2 mutations and other defects in DNA repair.
• Low-grade serous carcinoma. A slower-growing form that tends to occur in younger patients and responds differently to treatment than HGSC.
• Endometrioid carcinoma. Often associated with endometriosis. Frequently diagnosed at an earlier stage.
• Clear cell carcinoma. Also associated with endometriosis. Tends to be less responsive to standard chemotherapy.
• Mucinous carcinoma. A rare subtype that often forms large tumors. True primary ovarian mucinous cancers are uncommon and must be distinguished from cancers that have spread from the gastrointestinal tract.

Germ cell tumors

Germ cell tumors begin in the egg-producing cells of the ovary. They account for less than 5% of ovarian cancers and tend to occur in younger women and adolescents. Most are highly treatable. Types include dysgerminomas, yolk sac tumors, and immature teratomas.

Stromal tumors

Stromal tumors begin in the connective tissue cells that hold the ovary together and produce hormones. They are rare and often produce hormones such as estrogen or testosterone, which can cause symptoms like abnormal bleeding or changes related to hormones. The most common type is granulosa cell tumors.

Related cancers

Fallopian tube cancer and primary peritoneal cancer are closely related to epithelial ovarian cancer. They have similar risk factors, behave similarly, and are treated the same way. Most cancers historically labeled “ovarian” are now believed to begin in the fallopian tube.

Related conditions

Certain conditions can be associated with a higher risk of developing ovarian cancer:

• Endometriosis. A condition in which tissue similar to the uterine lining grows outside the uterus. Endometriosis is associated with an increased risk of certain types of ovarian cancer, particularly clear cell and endometrioid subtypes.
• Hereditary cancer syndromes. Inherited mutations in BRCA1, BRCA2, and Lynch syndrome genes (such as MLH1, MSH2, MSH6, PMS2) significantly increase the lifetime risk of ovarian cancer.