The ovaries are a pair of organs in the female reproductive system. They are in the pelvis, one on each side of the uterus (the hollow, pear-shaped organ where a fetus grows). Each ovary is about the size and shape of an almond. The ovaries make eggs and female hormones.

The fallopian tubes are a pair of tubes through which eggs travel from the ovaries to the uterus.  The peritoneum is the membrane lining the cavity of the abdomen and covering the abdominal organs.

Ovarian cancers are now known to be several distinct diseases, which are named after the type of cell they come from: epithelial, germ cell, and stromal.  These are the three main cell types that make up the ovary.  Each cell type can develop into a different type of tumor, and each type differs in how it spreads, how it’s treated and its prognosis.

• Epithelial ovarian cancer arises from the surface of the ovary (the epithelium), and is the most common ovarian cancer. Fallopian Tube Cancer and Primary Peritoneal Cancer are also included within this designation.

• Clear Cell is a type of ovarian cancer that gets its name because the center of the cells appears clear when viewed through a microscope. Clear cell tumors are uncommon and they typically occur in women in their 40’s and 50-70% of women who develop this type of cancer have endometriosis. Clear cell tumors are often diagnosed at Stage 1, but the survival rate for women with these tumors is generally lower because it is a more aggressive subtype.
• Germ Cell Ovarian Cancer arises from the reproductive cells of the ovaries and is rare.
• Stromal Cell Ovarian Cancer arises from connective tissue cells, is very rare.
• Small Cell Carcinoma (SCCO) of the ovary is an extremely rare ovarian cancer and it is not certain whether the cells in SCCO are from ovarian epithelial cells, sex-cord stromal cells or germ cells.

Not all ovarian tumors are cancer. Some ovarian tumors may be abnormal but not necessarily cancerous. Read more here.