Between 20 percent and 40 percent of women past age 35 have fibroids. These are noncancerous tumors of the uterus that appear during your childbearing years. Also called myomas, fibromyomas or leiomyomas, fibroids can appear on the inside or outside lining of your uterus, or within its muscular wall. They usually develop from a single smooth muscle cell that continues to grow. You may have a single fibroid or several.
Fibroids can range from pea sized to the size of a grapefruit.
Although most fibroids remain small, their growth can be unpredictable. Some grow slowly, while others may grow very quickly. Most of the time, however, fibroids aren't dangerous. They are not associated with an increased risk of uterine cancer and almost never develop into cancer. Fibroids can require emergency treatment if they cause sudden, sharp pelvic pain.