Endometrial stromal sarcoma of uterus

Endometrial stromal sarcomas are the second most common uterine sarcomas. Currently, they are classified into low-grade endometrial stromal sarcomas and undifferentiated endometrial sarcoma. Low-grade endometrial stromal sarcomas are biologically low-grade uterine sarcomas, and typically composed of uniform cells intimately associated with prominent arterioles, resembling the endometrial stroma in proliferative phase. There is usually little cytological atypia or pleomorphism, and mitoses are scanty. In contrast, undifferentiated endometrial sarcomas are frankly malignant, lack specific differentiation and any features of normal endometrial stroma. It is a highly aggressive neoplasm, often exhibiting myometrial invasion, haemorrhage and necrosis, as well as marked nuclear pleomorphism and high mitotic activity. The diagnosis of undifferentiated endometrial sarcoma is reached after excluding other uterine tumours with a sarcomatous component, such as adenosarcoma and malignant mixed Müllerian tumour. Histological variants of endometrial stromal sarcomas, including the so called ‘high-grade endometrial stroma sarcomas’ are addressed. The problems with histologic diagnosis and application of immunohistochemical studies and molecular pathology are highlighted.