The factors that predispose to endometrial cancer are not well worked out. However, the disease seems commoner in women who have experienced long periods of 'unopposed' oestrogen administration (e.g. long term oestrogen administration or granulosa cell tumours of the ovary). Such patients suffer from endometrial hyperplasia (an overgrowth of the uterine lining) and this is a predisposing causative factor for the development of uterine cancer. Pursuing the factor of 'unopposed' oestrogen exposure, nulliparous women and those with a long menstrual life (late menopause - after the age of 52) have a 2.5 times higher incidence of the disease. Other factors known to be associated with a higher incidence of the disease include obesity, diabetes mellitus, high blood pressure, endometrial hyperplasia (see above) and a family history of the disease or breast and/or colon cancer. The long term administration of the drug tamoxifen (used in the therapy of breast cancer) is associated with an increased incidence of endometrial cancer via promoting emndometrial hyperplasia; the risk is low circa 1 per 1000cases treated and in most incidences the beneficial effects in terms of breast cancer protection outweigh the risks associated with the drug's use on the uterine lining.