Most uterine cancer fall into one of three types, based on the cell they developed from:
- Endometrial stromal sarcomas develop in the stroma (supporting connective tissue) of the endometrium.
- Uterine leiomyosarcomas start in the muscular wall of the uterus. Uterine carcinosarcomas, also known as malignant mixed mesodermal tumors or malignant mixed müllerian tumors (MMMT), start in the endometrium and have features of both sarcomas and carcinomas. They are usually classified with uterine sarcomas, but some doctors believe they are more closely related to carcinomas.
Among this group of uterine cancers, carcinosarcomas are the most common, followed by leiomyosarcomas. Endometrial stromal sarcomas are the least common.