Uterine fibroids, or leiomyomata in medical terminology, are extremely common smooth muscle tumors of the uterus. For reasons that currently remain a mystery, a single cell in the uterus may begin to grow rapidly. The resulting tumor is called a fibroid. While it is possible that a fibroid tumor can become cancerous, this is extremely unlikely. When a uterus is cut open fibroids usually have a whorled appearance, somewhat similar to a cut onion.
Fibroids can occur in many locations throughout the uterus.
Pedunculated fibroids are attached to the outside of the uterus by a thick stalk, similar to the root of a plant. Some women have only one, small fibroid, while others have dozens of them. It is the combination of size, number, and location that can produce symptoms. It is impossible to predict who will get fibroids. In some cases a small or medium-sized fibroid will stay the same size, or even become smaller, but in other cases it may slowly grow and develop symptoms over time.