A lot of women have uterine fibroids at some point in their life. You may have even had them and never known it. That’s because they often don’t cause any pain or symptoms.

So if you can get them and not have side effects, how do you even know if you have them? And should you be concerned?

What Are They?

Uterine fibroids, which your doctor may call leiomyomas or myomas, are muscular tumors that can grow on your uterus. They rarely turn into cancer, and if you get them it doesn’t mean you’re more likely to get uterine cancer.

Fibroids can vary a lot in size, shape, and location. They can show up in your uterus, uterine wall, or on its surface. They can also attach to your uterus by a stalk- or stem-like structure.

Some are so small that your doctor can’t even see them with the naked eye. Others grow in big masses that can affect the size and shape of the uterus.

Uterine fibroids usually appear in women of childbearing age — generally between 30 and 40 years old, but they can show up at any age. They’re also more common in African-American women than in white women, and tend to show up earlier and grow quicker in African-Americans, as well. Doctors don’t know why that is.