Uterine fibroids are tumors made of connective tissue and smooth muscle. They grow slowly within the wall of the uterus or attached to the uterine wall.
Most fibroids are noncancerous.
In some rare cases, they may become cancerous. A uterine fibroid may be as small as a pea or as large as a grapefruit. As the fibroid grows, the uterus may become deformed or pushed aside. When the uterus is deformed or blocked by a growth, the resulting pressure may cause symptoms in the bladder or intestine, such as increased urination, constipation, or pain. Heavy menstrual periods may occur.