This paper presents a case of carcinosarcoma localized in the endometrial polyp inside the uterus of a 74-year-old patient. This carcinosarcoma was diagnosed in the first clinical disease stage. Postoperative treatment was conducted but was not followed by additional chemo or radiotherapy due to the fact that the illness was in the first clinical stage. Secondary deposits in the abdomen and in the pelvis appeared exactly six months after surgery. Illness progression was sudden causing death three months after the appearance of secondary deposits or nine months after the illness was detected, despite attempts with chemotherapic treatment. Although uterine carcinosarcomas account for three to seven percent of all uterine malignities while malignant polyp degeneration occurs in only 0.36% cases, treatment of this malignant disease is a special challenge to all those involved in oncological gynecological practice with the aim of prolonging the progression-free interval and the overall survival of patients suffering from this rare malignity.