How often are uterine polyps cancerous?

According to the Mayo Clinic, uterine polyps are often non-cancerous, or benign. Also known as endometrial polyps, uterine polyps are growths on the inner wall of the uterus that extend into the uterine cavity. They are caused by an overgrowth of cells within the uterine lining.

The Mayo Clinic elaborates that uterine polyps range in size from a few millimeters up to that of a golf ball or larger. A woman may have a variable amount of uterine polyps, ranging from one to several. Although most commonly bound to the location of the uterus, these polyps may move through the cervix and into the vagina.