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Leiomyomata Uteri

Leiomyomata uteri are benign smooth muscle tumors of the uterus. They are also referred to as fibroids and uterine myomas. Myomas are the most common pelvic tumor in women, occurring in 20% of women of reproductive age. About 30% of hysterectomies are performed because of myomas.

Etiology

A small number of genes have been determined to have mutated in uterine myomas. Mutations in these genes may cause uterine myomas. Myomas were discovered to be monoclonal tumors both by glucose-6-phosphate dehydrogenase isoform analysis and Myomas also were discovered to contain nonrandom cytogenetic abnormalities. Approximately 45% of myomas are cytogenetically abnormal, with normal fibroid karyotypes observed in normal myometrium from the myoma of the same woman. The most frequently affected chromosomes are 1, 6, 7, 12, and 14. The most frequently reported cytogenetic abnormalities in myomas

The relationship between leiomyomas and leiomyosarcomas remains uncertain. Of women with a preoperative diagnosis of uterine myoma, fewer than 0.5% are discovered to have a leiomyosarcoma. Most leiomyosarcomas occur in uteri with coexisting myomas. In some cases, leiomyomas and coexisting leiomyosarcomas share the same cytogenetic abnormality [eg, del (7)(q22q32)]. These data support the concept that the evolved, through additional mutations, from the myoma. However, in many cases leiomyosarcomas contain clonal cytogenetic abnormalities that are not commonly seen in (rearrangement of band 10q22). In these cases it may be that the development of the sarcoma involved a genetic event that was independent of events leading to the development of the myomas.

Recent epidemiologic studies indicate that the peak occurrence of myomas is in women between 40 and 45 years of age. African-American women appear to have a threefold increase in the risk of developing myomas compared with white, Asian, and Hispanic women. The mechanisms that account for the high rate of myomas in African-American women are unknown. Pregnancy appears to protect against the development of fibroids.