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Cancer occurs when cells undergo a transformation and begin to grow and
multiply without normal controls. As the cells grow and multiply, they
form masses called tumors. Cancer is dangerous because it overwhelms healthy
cells by taking their space and the oxygen and nutrients they need to
survive and function.
Ovarian cancer occurs when a tumor forms in one or both of a woman's ovaries.
The ovaries are a pair of small organs that produce and release ova, or
human eggs. The ovaries also produce important hormones such as estrogen
and progesterone. They are located in the lower abdomen (pelvis), on either
side of the womb (uterus). Ova released by the ovaries travel through
the fallopian tubes to the uterus, where they may or may not be fertilized
by the male sperm.
Cancerous tumors are malignant. This means they spread to other tissues
and organs. Not all tumors, however, are malignant.
In a process called metastasis, malignant tumors may encroach on and invade
neighboring organs or lymph nodes, or they may enter the bloodstream and
spread to remote organs such as the liver or lungs. Metastatic tumors
are the most aggressive and serious of all tumors. The type of cell that
originated the abnormal growth determines the class of the ovarian tumors.
- Epithelial tumors: These tumors arise from a layer of cells that
surrounds the outside of the ovary called the germinal epithelium. About
70-80% of all ovarian cancers are epithelial. These are most common
in women who have been through menopause (aged 45-70 years).
- Stromal tumors: Stromal tumors develop from connective-tissue cells
that help form the structure of the ovary and produce hormones. Usually,
only one ovary is involved. These account for 5-10% of ovarian cancers.
These tumors typically occur in women aged 40-60 years. Often, surgical
removal of the tumor is the only treatment needed. If the tumor has
spread, though, the woman needs chemotherapy.
- Germ cell tumors: Tumors that arise from germ cells (cells that produce
the egg) account for about 15% of all ovarian cancers. These tumors
develop most often in young women (including teenaged girls). Although
90% of women with this type of cancer are successfully treated, many
become permanently infertile.
- Metastatic tumors: Only 5% of ovarian cancers have spread from other
sites. The most common sites from which they spread are the colon (52%),
breast (17%), stomach (10%), and pancreas (5%).
- Within these main classes are many different subtypes of tumors.
Noncancerous (benign) ovarian masses include abscesses or infections,
fibroids, cysts, polycystic ovaries, endometriosis-related masses, ectopic
pregnancies, and others.
- Of markedly enlarged ovarian masses (>4 cm) found in women who are
still menstruating (have not been through menopause), about 20% are
cancerous.
- Of markedly enlarged masses found in women who have been through
menopause, about 45-50% are cancerous.
The incidence of ovarian cancer varies greatly. Globally, Scandinavia,
Israel, and North America have the highest rates. Developing countries
and Japan have the lowest rates.
- At least 15,000 women die each year from ovarian cancer.
- The 5-year survival rate is greater than 75% if diagnosis of the
cancer occurs before it has spread to other organs. However, the 5-year
survival rate drops to 20% when the tumor has spread to the upper abdomen.
- In the United States, about 1 in 56 women develops cancer of the
ovary. More than 26,000 new cases are diagnosed each year.
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