The inside of the uterus is covered with a layer of cells called endometrium. At the beginning of each menstrual cycle, the endometrium thickens to possibly host an embryo at implantation. If at the end of the menstrual cycle, no embryo implants, much of the uterine lining peels off, thus constituting the menstrual period.
Unfortunately, sometimes due to environmental, chemical or physical factors, or certain viruses, certain cells lining the inside of the uterus multiply without control, and form cancerous growth. In another words, you have cancer of the uterus when DNA gene of a group of cells that line the inner of your uterus is damaged or changed in such a way that they reproduce anarchically to form a malignant growth.
Estrogen levels play a major role in the development of uterine cancer. Although several factors may influence the increased estrogen levels, obesity and menopause are the two major causative factors. There is no strong relationship between uterine cancer and STDs. The cancer can occur in women who have never had any sexual intercourse or HPV infection. Uterine cancer is more common among women who had few or no children.