Carcinosarcoma of the uterus is a biphasic neoplasm composed of malignant epithelial and mesenchymal elements. They typically arise within the endometrial cavity but, in rare cases, neoplasms may arise in the cervix or within an endometrial polyp.
Although carcinosarcoma is the preferred term for this group of tumors, according to the International Society of Gynecological Pathologists (ISGyP)/World Health Organization (WHO) classification, it is also referred to as malignant mixed müllerian tumor.
These tumors are currently thought to be monoclonal carcinomas with sarcomatous differentiation.
Various synonyms have been used to distinguish those with only homologous mesenchymal elements (carcinosarcoma) from those with only heterologous mesenchymal elements (malignant mesodermal mixed tumor or malignant müllerian mixed tumor [MMMT]).