Leiomyoma (Uterine Fibroids)
Leiomyomas are benign, smooth muscle tumors of the myometrium. They are the most common uterine tumors in women of reproductive age, occurring in up to 70% of women by age 50.
1. Pathogenesis & Classification
- Hormone Dependence: Growth is estrogen-sensitive. Tumors increase in size during pregnancy and shrink after menopause.
- Location Matters:
- Intramural: Within the myometrium (most common).
- Submucosal: Projecting into the endometrial cavity (often causes the most abnormal uterine bleeding).
- Subserosal: Projecting from the outer surface of the uterus.
2. Histology & Clinical Findings
| Finding | Details |
|---|---|
| Histology | Whorled pattern of smooth muscle bundles; no significant atypia. |
| Clinical Triad | Menorrhagia, pelvic pressure, and an irregularly enlarged uterus on exam. |
3. Exam Must-Knows
- Leiomyosarcoma: Rare, malignant counterpart. Unlike leiomyomas, these arise de novo (not from pre-existing fibroids), are found in postmenopausal women, and show high mitotic index/necrosis.
- Infertility: Especially with submucosal lesions, as they interfere with implantation.
Pathology Board Hint: For board exams, distinguish between leiomyoma (benign, whorled muscle, reproductive age) and leiomyosarcoma (malignant, necrosis/mitosis, postmenopausal). If a vignette describes a “firm, irregular mass” in a premenopausal woman with heavy periods, think fibroids.