Ovarian cancer is cancer that develops in the ovaries, the two small organs on either side of the uterus, which produce ova (eggs) as well as secrete the female hormones estrogen and progesterone. Ovarian cancer is mainly seen in post-menopausal women but it can occur at any age. Although rare, more women die from ovarian cancer than from uterine cancer and cervical cancer put together because it usually causes few symptoms in the early stages. Those symptoms that do develop are often vague and may mimic those of digestive disorders, such as abdominal pain, discomfort or distension, and are likely to be overlooked.
There are different types of ovarian cancers but the three main types are :
- epithelial tumors arising from the surface epithelial cells
- germ cell tumors from cells that produce ova
- stromal tumors from connective tissue cells
These are all primary tumors of the ovary, originating in the ovary itself. Secondary tumors may occur in the ovaries from spread of cancer from different organs of the body. The most common primary cancers that metastasize to the ovary are cancers of the breast, uterus, stomach, and colon.
Although the exact cause of ovarian cancer is not known, a faulty genetic factor has been linked to ovarian cancer, namely mutations in BRCA1 and BRCA2 genes. The process of developing cancer is further explained under what is cancer and benign vs malignant tumors. A combination of surgery and chemotherapy is the usual choice of treatment. The role of radiation therapy in the treatment of ovarian cancer is limited, but it may be considered in selected cases.
The ovaries are a pair of small, oval shaped organs, about 2.5 to 5 cm in length, situated in the pelvis, close to the pelvic wall and on either side of the uterus. The upper part of the ovary lies close to the fimbriated end of the fallopian tube. It is usually pinkish-grey in appearance with a rough, uneven surface, and areas of scar tissue. The ovary is suspended by means of 3 ligaments – the mesovarium, the suspensory ligament of the ovary, and the ovarian ligament.
The ovary is covered by low columnar epithelium and consists of the outer cortex and the inner medulla. The medulla is composed of connective tissue fibers, muscle cells, lymphatic and blood vessels, nerves, and supporting tissue. The cortex is made up of the stroma with many vessels and scattered follicles of epithelial cells within it.
The follicles contain ova or eggs in various stages of maturity. The more mature follicles, known as the Graafian follicles, enlarge and project on to the surface of the ovary. When a Graafian follicle becomes fully mature, it bursts to release the ovum. This is known as ovulation. The remains of the Graafian follicle is known as the corpus luteum, which is eventually replaced by scar tissue, which may be seen on the surface of the ovary. If the ovum gets fertilized by a sperm, it forms the embryo, which eventually develops into the fetus.
The ovaries are also responsible for producing and secreting the female hormones estrogen and progesterone. These hormones are responsible for the development of sexual characteristics in a woman, as well as regulating menstruation and pregnancy. During and after menopause, the ovaries stop producing eggs, and hormone production also decreases.
Spread of Ovarian Cancer
When cancer cells break off and spread to other parts of the body, it is known as metastasis. In ovarian cancer, metastasis may occur in the following ways :
- Ovarian cancer can spread by local extension or direct contact into the adjacent tissues and organs, such as the uterus, fallopian tubes, bladder, or rectum.
- Intraperitoneal dissemination is very common, where the cancerous cells are shed into the peritoneal cavity and carried by the peritoneal fluid and deposited within the pelvic or abdominal cavity and the peritoneal lining.
- The other means of spread is by lymphatic vessels to distant sites such as the lungs and the liver. Invasion of the diaphragmatic lymph vessels by cancer cells is common in advanced stages resulting in ascites (accumulation of fluid in the abdominal cavity), and the development of pleural effusion due to transdiaphragmatic spread.
- Hematogenous spread occurs when cancer cells travel through the blood stream but is uncommon in ovarian cancer.