What is a leiomyomatous uterus?

What is a Leiomyomatous Uterus?

A leiomyomatous uterus is a uterus containing one or more leiomyomas (also called fibroids or myomas), which are benign smooth muscle tumors arising from the myometrium and represent the most common gynecologic tumors in women. 1

Definition and Pathophysiology

• Leiomyomas are benign, sex steroid-responsive clonal expansions of individual myometrial smooth muscle cells that form distinct nodular tumors with clear demarcation from surrounding normal myometrium. 1

• The histology is virtually indistinguishable from normal myometrium, with highly variable cellularity and areas of fibrosis and calcification often interspersed, especially after degeneration or in postmenopausal women. 1

• These tumors grow in a spherical nodular fashion, reflecting their clonal origin from individual smooth muscle cells and fibroblasts. 1

Epidemiology and Clinical Significance

• Uterine leiomyomas are by far the most common benign tumors of the female genital tract and likely the most common soft-tissue tumors in the entire body, with estimates as high as 70% of women having identifiable leiomyomata present in their uterus at menopause. 1

• Approximately 200,000 hysterectomies and 20,000 myomectomies are performed annually in the United States because of symptoms caused by leiomyomata. 1

• Leiomyomata are more common in African-American women, who have an estimated incidence exceeding 80% by age 50, compared to approximately 70% in White women. 1

Clinical Presentation

The clinical presentation is highly variable:

• Many women remain completely asymptomatic despite having leiomyomas, as the incidence far exceeds the frequency of clinical problems attributable to them. 1

• Symptomatic presentations include:

  • Menometrorrhagia (heavy and prolonged uterine bleeding), which can lead to anemia 1
  • Dysmenorrhea (painful menstruation) 1
  • Pelvic pain and pressure 1
  • Reproductive failure and infertility 1
  • Compression of adjacent pelvic viscera causing urinary urgency, frequency, or constipation 1

• Size does not correlate with symptoms: tumors can attain very large size with few if any symptoms, while small leiomyomata may cause massive uterine bleeding and pain. 1

Important Clinical Considerations

Malignancy Risk

• Leiomyomas are almost invariably benign and should be considered benign in premenopausal women. 1

• Leiomyosarcomas (malignant transformation) comprise only 0.1% of all uterine tumors, but increase to 1.7% of women undergoing hysterectomy for leiomyomata in their seventh decade of life. 1

• Histologic criteria for malignancy include increased numbers of mitoses, cellular pleomorphism, and thrombotic degeneration within the tumor. 1

Pregnancy Considerations

• Leiomyomatous uterus is significantly associated with preterm birth (adjusted odds ratio 2.5; 95% CI 1.7-3.7), and this association persists even after myomectomy. 2

• When rapid growth occurs, as occasionally observed in pregnancy, the central area of individual tumors may undergo necrosis and be replaced by hyalinized degeneration. 1

Genetic and Molecular Features

• Leiomyomas have a non-Mendelian inheritance pattern with genetic predisposition. 1

• Approximately one-third of individual leiomyomas have some type of clonal chromosomal aberration, though this is not consistent between individual leiomyomata, even in the same woman. 1

• The pathogenesis involves a complex interaction of genetic mutation, endogenous sex-steroid production, reproductive patterns, and environmental and medicinal hormonal exposure. 1

Natural History

• Many leiomyomata have limited growth potential and remain static in size until the reproductive age level of sex steroids declines at menopause. 1

• Fibroid-associated symptoms peak in the perimenopausal years and typically decline after menopause. 1