This Publication Is Searchable The Merck Manual of Diagnosis and Therapy Section 18. Gynecology And Obstetrics Chapter 240. Benign uterine tumors of smooth muscle origin. In the uterus, submucosal, intramural, and subserosal sites are the most common.
Fibroids are usually multiple.
Some are pedunculated. Fibroids are monoclonal, probably arising from a single smooth muscle cell. Because they have estrogen receptors, they tend to increase in size during the reproductive years and regress after menopause. Although patients are often concerned about cancer in fibroids, sarcomatous change is extremely rare. Degeneration or growth of a fibroid causes acute pain that can become chronic, with continuing degeneration.