Fibroids are the most common tumors of the female reproductive system. Also known as uterine myomas, leiomyomas, or fibromas, fibroids are firm, compact tumors that develop in the uterus. They are made of smooth muscle cells and fibrous connective tissue.
It is estimated that 20 to 50 percent of women of reproductive age have fibroids, although not all are diagnosed. According to some estimates, 30 to 77 percent of women will develop fibroids sometime during their childbearing years, although only about one-third of these fibroids are large enough for a physician to detect. They may range in size from the size of a pea to the size of a softball or small grapefruit.
In more than 99 percent of fibroid cases, the tumors are benign (non-cancerous). The tumors are not associated with cancer and do not increase a woman's risk for uterine cancer.
For more information, see the Yale Medical Group's Uterine Fibroids online health resource.