Normal Anatomy and the Development of Ovarian Cancer

The ovaries are part of the female reproductive system. They are two small, oval-shaped organs found inside the pelvic region on each side of the uterus. The main functions of the ovaries are to produce eggs and hormones (estrogen and progesterone) that control sexual development, reproduction, ovulation, and the menstrual cycle. As part of the menstrual cycle, ovarian cells shed in the peritoneum, a double-layered, fluid-filled membrane that surrounds and supports the abdominal cavity.

Each ovary is surrounded by a capsule and has 3 different types of cells:

• Epithelial—The outermost layer that covers the ovary.
• Germ—These cells are inside the ovary and develop into eggs.
• Stroma—The connective tissue of the ovary.

Cell division and growth is a normal process in the body to replace old or damaged cells. Changes in hormones, which may or may not be affected by genetic abnormalities, cause changes in ovarian cells. These changes can alter the DNA of the cells which tells them when to grow and when to stop. Normally the cells only grow enough to replace old or damaged cells, but damaged DNA may cause the abnormal growth of cells, known as cancer.

Ovarian cancer can start anywhere in the ovarian tissue, but the most common place is in the epithelial cells that cover the ovary. Ovarian cancer can spread directly to nearby structures in the abdominal cavity. The cancer can also spread to adjacent lymph nodes or blood vessels, which can carry cancer cells to other areas of the body. The most common sites for ovarian cancer to spread outside of the abdomen are to lymph nodes in other parts of the body, lungs, liver, and bones.

Cancer in the Left Ovary

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Types of Ovarian Cancer

Ovarian cancer is characterized by where tumors start, where they grow, and their appearance under a microscope. Ovarian cancer types include:

• Epithelial carcinoma —Makes up nearly 90% of ovarian cancers. There are eight different subtypes of epithelial carcinomas that differ on how they look under a microscope. The most common type of epithelial carcinoma is called serous.
• Germ cell tumors —Tumors in the cells that produce eggs.
• Stromal tumors —Tumors in the connective tissue that supports the ovary.