Malignant pure mesenchymal uterine tumours encompass endometrial stromal sarcoma (ESS), uterine leiomyosarcoma, and undifferentiated sarcomas. This Review discusses pathology, preoperative diagnosis, and standard treatment of uterine leiomyosarcoma and low-grade ESS (distinct from undifferentiated uterine sarcomas), with an emphasis on targeted treatment. We show that several features on ultrasonography and MRI can raise suspicion of a uterine sarcoma; however, there are no pathognomonic features on any imaging technique. For both ESS and uterine leiomyosarcoma, hysterectomy with bilateral salpingo-oophorectomy, but without lymphadenectomy, is the standard surgical treatment for early stage disease. The clinical benefit of chemotherapy is limited, which underscores the importance of targeted therapy. ESS and uterine leiomyosarcoma are driven by different pathways, resulting in a different clinical behaviour. ESS typically is a hormone-sensitive tumour with indolent growth. Uterine leiomyosarcoma is notorious for its aggressive growth and poor outcome. Individualisation of treatment is mandatory, because randomised trials are almost non-existent. The progesterone and oestrogen receptors are clinically important targets for most primarily advanced or recurrent ESS and a subset of recurrent uterine leiomyosarcomas. Potential future targets and targeted treatments that are under investigation are presented for both entities.