Risk factors for uterine sarcomas are Prior pelvic radiation Tamoxifen use Uterine sarcomas include Leiomyosarcoma (the most common subtype [63%]) Endometrial stromal sarcoma (21%) Undifferentiated uterine sarcoma Rare uterine mesenchymal sarcoma subtypes include Adenosarcomas Perivascular epithelioid cell tumor (PEComas) Rhabdomyosarcoma Carcinosarcomas used to be categorized as sarcomas but are now considered and treated as high-grade epithelial tumors (carcinomas).