The cause of death for actress Loni Anderson has been confirmed less than three weeks after she died at age 79. Anderson died of metastatic uterine leiomyosarcoma, a rare form of cancer, according to a death certificate obtained by TMZ on Friday, August 22. The death certificate doesn't list any other contributing factors. According to the National Organization for Rare Disorders, uterine leiomyosarcoma begins in the uterus and can spread "to other areas of the body, especially the lungs and liver," which often causes "life-threatening complications.