The uterus is a hollow, muscular organ where a fetus grows. Uterine cancer can start in different parts of the uterus. Most uterine cancers start in the endometrium (the inner lining of the uterus). This is called endometrial cancer. Most endometrial cancers are adenocarcinomas (cancers that begin in cells that make mucus and other fluids).
Uterine sarcoma is an uncommon form of uterine cancer that forms in the muscle and tissue that support the uterus.
Obesity, certain inherited conditions, and taking estrogen alone (without progesterone) can increase the risk of endometrial cancer. Radiation therapy to the pelvis can increase the risk of uterine sarcoma. Taking tamoxifen for breast cancer can increase the risk of both endometrial cancer and uterine sarcoma.
The most common sign of endometrial cancer is unusual vaginal bleeding. Endometrial cancer can usually be cured. Uterine sarcoma is harder to cure.