Uterine sarcoma accounts for 3 to 9 percent of all uterine malignant neoplasms [1,2]. Uterine sarcomas arise from dividing cell populations in the myometrium or connective tissue elements within the endometrium. Compared with the more common endometrial carcinomas (epithelial neoplasms), uterine sarcomas, particularly leiomyosarcomas (connective tissue neoplasms), behave aggressively and are associated with a poorer prognosis. (See "Endometrial carcinoma: Pretreatment evaluation, staging, and surgical treatment".)
The classification, clinical manifestations, and staging of uterine sarcomas that arise in adults (eg, endometrial stromal sarcomas, leiomyosarcoma, adenosarcoma) are reviewed here. Staging and treatment of endometrial stromal tumors and leiomyosarcoma are discussed separately. Carcinosarcoma, which is no longer classified as a sarcoma, and rhabdomyosarcoma, which typically arises in children and adolescents, are also discussed separately. (See "Treatment and prognosis of uterine leiomyosarcoma" and "Classification and treatment of endometrial stromal tumors" and "Clinical features, diagnosis, staging, and treatment of uterine carcinosarcoma" and "Rhabdomyosarcoma and undifferentiated sarcoma in childhood and adolescence: Epidemiology, pathology, and molecular pathogenesis".)
The World Health Organization and College of American Pathologists (table 1) have published classification systems for uterine sarcomas. The histologic classification of these neoplasms is based upon the differentiation/growth pattern of the neoplastic cells and their presumed cell of origin.
Uterine sarcomas are referred to as homologous or heterologous. The majority are homologous (ie, differentiate in ways similar to normal uterine tissues), including endometrium (endometrial stromal sarcomas), muscle (leiomyosarcoma), or sarcomas of nonspecific supporting tissue (eg, connective tissue, blood vessels, lymphatics). In contrast, heterologous tumors contain elements with non-native differentiation (eg, skeletal muscle, cartilage, bone).
Historically, uterine carcinosarcoma was classified as a type of uterine sarcoma and was termed malignant mixed müllerian tumor or mixed mesodermal sarcoma. However, these neoplasms are now classified as carcinomas since they derive from a monoclonal neoplastic cell, which has more characteristics of epithelial than stromal neoplasms. In addition, the epidemiology, risk factors, and clinical behavior associated with carcinosarcoma suggest a closer relationship to endometrial carcinoma than to sarcoma. (See "Clinical features, diagnosis, staging, and treatment of uterine carcinosarcoma".)