Uterine leiomyosarcoma

Uterine leiomyosarcoma (LMS) is a rare malignant smooth muscle tumor arising from the myometrium. It accounts for < 5% of uterine sarcomas but is one of the most common uterine sarcomas. Unlike benign leiomyomas (fibroids) which are extremely common, LMS is aggressive and difficult to diagnose preoperatively. Diagnosis is pathological; features include mitotic rate > 10 mitoses per 10 high-power fields, tumor cell necrosis, and cellular atypia. Risk factors include prior pelvic radiation and possibly prior myomectomy or uterine artery embolization (debated). Presentation is similar to benign fibroids: abnormal uterine bleeding, pelvic pain, pelvic mass on examination or imaging. However, LMS often presents at an advanced stage with metastases (lungs are most common site). Imaging (ultrasound, MRI) cannot reliably distinguish LMS from leiomyoma; rapid growth or heterogeneous appearance raises suspicion. Definitive diagnosis requires biopsy and pathological analysis. Staging uses FIGO staging (extent of myometrial invasion, cervical involvement, and metastases). Prognosis is poor: 5-year overall survival is ~40% (varies by stage and grade). Treatment is surgery (total hysterectomy ± bilateral salpingo-oophorectomy for ovarian staging); role of chemotherapy is controversial. Adjuvant radiation may be considered for high-risk disease. Surveillance includes follow-up imaging to detect metastases. Board relevance: always consider sarcoma in premenopausal women with rapidly enlarging uterine mass.