BACKGROUND Making a histologic diagnosis of leiomyosarcoma in the specimen from a hysterectomy performed for suspected benign fibroids is rare. Currently, there are no reliable diagnostic tools to diagnose uterine sarcomas preoperatively. CASE A 38-year-old woman presented with menorrhagia and a uterine fibroid measuring 6.0 cm x 8.1 cm x 6.2 cm on ultrasonography. The patient underwent a laparoscopic myolysis with 50% shrinkage of the fibroid volume at follow-up after six months. Six years after myolysis, the patient presented with right lower quadrant pain and a rapidly enlarging uterus. Hysterectomy and bilateral salpingo-oophorectomy was performed and a diagnosis of leiomyosarcoma was histologically confirmed. CT scan was performed biannually after hysterectomy. One year after surgery, the patient presented with radiologic evidence of a right pulmonary nodule. The nodule was excised thoracoscopically and histologic examination demonstrated metastatic leiomyosarcoma. One year later, another pulmonary lesion appeared in the left lung and was excised thoracoscopically. Again, histological assessment showed metastatic leiomyosarcoma. This patient has remained healthy and asymptomatic for two years since the last thoracoscopic excision of the leiomyosarcoma metastasis. CONCLUSION The current trend in treatment for symptomatic fibroids is therapy sparing the uterus. Such treatment includes both medical therapy and fibroid necrosing therapies such as vascular occlusion, embolization, and thermal coagulation technologies. Women considering uterus-sparing treatment should be advised of the potential risk of uterine malignancy, even though that risk is quite minimal (< 0.5%). A delay in the diagnosis of uterine malignancy may ultimately compromise long-term survival.