A fibroid in the uterus is a noncancerous tumor that grows in or on the wall of the uterus. Fibroids are made up of muscle and connective tissue from the wall of the uterus and can vary in size from being so tiny that you cannot see them with the naked eye to being the size of a melon. They can be located in different parts of the uterus, including the muscle wall of the uterus, just under the surface of the uterine lining, just under the outside lining of the uterus, or on a long stalk on the outside or inside the uterus. Fibroids can cause a range of symptoms, including heavy or prolonged periods, bleeding between periods, pelvic pain, frequent urination, and low back pain. However, most women with fibroids do not experience symptoms. Fibroids are almost always benign and are not associated with an increased risk of uterine cancer.