Prevalence

Leiomyomata, commonly referred to as fibroids, are the most common tumors of the female genital tract. Their prevalence is impossible to fully assess as many do not come to clinical attention. However, rates are frequently stated to be over 40% in women 40 years or older. With more systematic evaluation, higher rates have been noted. Sixty-nine percent of women who underwent a hysterectomy for noncancerous conditions in Maryland, USA, were found to have fibroids, approximately half of which were not suspected prior to surgery.

With scrupulous histologic examination, fibroids were found by Cramer and Patel in 77 of 100 consecutive hysterectomy specimens. Prevalence reported by histology may reflect only those tumors associated with symptoms rather than a true estimation of their occurrence. In fact, histologically confirmed tumors may only represent 29% of patients for whom sonographic evidence of fibroids exists.

In 1998, a study was undertaken to determine the prevalence of occult fibroids in a random sample of premenopausal women using vaginal ultrasonography. A high percentage (62%) of these women were found to have sonographic evidence of fibroids. However, only 5.4% of 335 Swedish women were found to have fibroids on ultrasonographic examination. Additionally, the occurrence was only 10.1% in 11258 Japanese women. It is clear that though fibroids are a very common pathology, the exact prevalence rate may be impossible to ascertain and may have some significant ethnic and/or environmental associations.