Normally, the lining of the uterus (endometrium) builds up and then sheds every month. You know this shedding as menstrual bleeding. In most cases of endometrial cancer, the endometrium has built up, or thickened, and has stayed that way. This is called endometrial hyperplasia. From this "precancer" stage, the cells can grow quickly and out of control. These fast-growing cells are cancer cells.

As the cancerous cells multiply, they form a mass of tissue. Some of this tissue mass passes out of the uterus through the cervix and vagina as part of abnormal bleeding. Abnormal bleeding occurs in 90% of women with endometrial cancer.³

If endometrial cancer is not treated, it may spread from the uterus into deeper layers of the connective tissue around the uterus. As it progresses, it may spread to the pelvic lymph nodes and other pelvic organs. Advanced-stage cancer may spread to lymph nodes, to other organs in the pelvis, causing problems with kidney and bowel function, or to other organs in the body, such as the liver and lungs. The most common sites for spread (metastasis) of endometrial cancer are the vagina, lungs, and abdominal cavity.⁴

The stage and grade of your cancer is one of the most important factors in selecting the treatment option that is right for you. The long-term outcome (prognosis) depends on the stage of your cancer. The stage of you cancer will be determined by what your doctor finds at the time of surgery. The grade of your cancer is determined by how the cancer cells look under the microscope.

Endometrial cancer is the most common type of women's pelvic cancer.² Uterine sarcoma is a less common type of uterine cancer. For more information, see the following topics:

• Endometrial Cancer - Health Professional Information [NCI PDQ]
• Endometrial Cancer - Patient Information [NCI PDQ]
• Uterine Cancer, Sarcoma - Health Professional Information [NCI PDQ]
• Uterine Cancer, Sarcoma - Patient Information [NCI PDQ]