Malignant mixed Mullerian tumor (MMMT) is a rare uterine sarcoma or carcinosarcoma occurring in the female abdominal cavity. Because it is so rare (and nobody famous has died of it), there is little research on MMMT. The current thinking is that it might not be related to endometrial cancer, one speculation being that it might be a cancer of the Stem cells, because the body starts producing spindle cells in an out-of-control fashion.