Low-grade stromal sarcomas are usually slow growing and tend to remain confined to the uterus in about 70 percent of cases. Spread beyond the uterus occurs via the lymph system or via the bloodstream. High-grade stromal sarcomas spread in similar ways, but they behave much more aggressively and are usually advanced at the time of diagnosis.
What Causes It The exact cause is unknown. Like the more common endometrial carcinoma , heterologous mixed mesodermal tumors appear to be associated with diabetes, hypertension and obesity. There is also a significant association with previous pelvic radiation (10 to 30 percent of cases). The average time interval between pelvic radiation and the development of the sarcoma is 15 to 20 years.
Unlike other uterine sarcomas, leiomyosarcomas have no association with previous pelvic radiation.
