Uterine cancer occurs in two main forms depending on the part of the uterus involved. The most common type is cancer of the endometrium, which accounts for more than 95 percent of uterine cancer cases, according to The M.D. Anderson Cancer Center. The other form is uterine sarcoma. The National Cancer Institute says that uterine cancer makes up 6 percent of all cancers in women in the U.S.
Endometrial Cancer
The lining of the uterine wall is called the endometrium. Endometrial adenocarcinoma is the most common type of endometrial cancer, accounting for more than 80 percent of cases, according to Merck.com. This cancer usually begins with a thickening of the uterine walls. Abnormal bleeding in a premenopausal woman, or any bleeding in a postmenopausal woman can be an early sign of uterine cancer. Endometrial cells found on a pap test from a postmenopausal woman, or atypical cells from any woman, are also possible indicators of uterine cancer.
Other Types of Endometrial Cancer
Other types of endometrial cancer are papillary serous and clear cell adenocarcinoma. These rare forms of endometrial cancers are usually found at a later stage than the main type, and have a less favorable outlook, according to Oncolink.org. Together they comprise approximately 15 percent of all endometrial cancers. These cancers are not related to increased levels of estrogen as is the more common form.
Uterine Sarcomas
Sarcomas of the uterus are cancers of the muscle or connective tissue of the uterus and account for only about 2 percent of all uterine cancer, says the University of Maryland Cancer Center (UMCC). They are aggressive, and have a poor prognosis compared to endometrial cancer, reports Merck.com. There are three types of uterine sarcomas: carcinosarcoma, leiomyosarcoma and endometrial stromal sarcoma. Carcinosarcomas, the most common of the three, develop in the inner lining of the uterus and stromal sarcomas grow in the connective tissue of the lining. Leiomyosarcomas are cancers of the smooth muscle cells of the uterus, according to UMCC.
Causes
Although the causes of uterine cancer are not known, several risk variables have been identified. Increased levels of estrogen due to such factors as hormone replacement without progesterone, tamoxifin use and obesity, are all related to a higher risk of developing uterine cancer. A woman beginning her period early in life and reaching menopause late results in greater estrogen exposure, and is also a risk factor. Additionally, diabetes, high blood pressure and a family history of uterine cancer are associated with an increase in risk, according to Merck.com.
