Uterine cancer is a slow-growing malignancy that affects the uterus of a woman who is usually, though not always, over 50 years of age. It should not be confused with benign conditions of the uterus, which include fibroids, endometriosis, and endometrial hyperplasia (which can develop into cancer and thus may be cause for a hysterectomy). The most common cancer of the uterus begins in the endometrium or lining of the uterus; it is called uterine cancer or endometrial cancer, and is one of the leading cancers in women, though not usually fatal. A much less common kind of cancer can develop in the myometrium or muscle of the uterus; this is called uterine sarcoma. Cancer can also begin in the cervix; this common but rarely fatal cancer is known as cervical cancer.
Besides age and endometrial hyperplasia, the biggest risk factor for endometrial cancer seems to be prolonged exposure to estrogen. Women who had their first periods early and have never been pregnant have had higher exposure to estrogen than normal and thus are considered at higher risk for endometrial cancer. Women over 50, who are generally postmenopausal, are exposed to estrogen from body fat, hormone replacement therapy (HRT), or tamoxifen. So obese women are considered at higher risk, as are those whose HRT contained estrogen without progesterone. In addition, women with colorectal cancer have a higher risk of developing uterine cancer. If any of these apply to you, don't become filled with dread: just because you are at higher risk doesn't mean you will inevitably develop the disease.
Happily, uterine sarcoma is much more rare than uterine or endometrial cancer. The risk factors are not well understood, but women who have had pelvic radiation seem to develop more uterine sarcomas than other women. In addition, the risk factors for all cancers overlap to a degree. These risk factors are lifestyle based, and include smoking, poor diet (especially a diet high in saturated fats), lack of exercise, and stress. Eating well, exercising, and quitting smoking will reduce anyone's risk of cancer.
While abnormal menstrual bleeding is a sign of perimenopause, it can also be a symptom of uterine cancer, and should be cause for a visit to the doctor. Other symptoms include pain in the pelvic area and painful or difficult urination or intercourse. If you have such symptoms, a doctor will normally perform a pap smear (a better test for cervical than uterine cancer) and pelvic exam, and possibly also transvaginal ultrasound, a biopsy, and/or the dreaded dilation and curettage (D&C). The doctor will try to determine the stage of the cancer in order to decide on the best treatment. Uterine cancer has several stages: it may only be in the body of the uterus, it may have spread to the cervix, it may have spread through the pelvis, or in the worst case, it may have spread beyond the pelvis to other body parts. In the first two stages the most reliable treatment is hysterectomy (usually with oophorectomy and salpingectomy), but if the cancer has metastasized, most doctors recommend radiation therapy or chemotherapy. In some cases, hormone therapy using progestin, a synthetic progesterone, may be recommended.
Some good internet information sources on endometrial cancer can be found at
cancernet.nci.nih.gov/wyntk_pubs/uterus.htm
www.mayoclinic.com/home?id=DS00306
There's good info on uterine sarcoma at
cancernet.nci.nih.gov/cancer_types/uterine_sarcoma.shtml | 
