We present the case of a 56-year-old woman presenting an uterine tumor associated with pain and vaginal bleeding. The slides from the tumor were studied with monoclonal antibodies to Vimentin, CD 10, KL 1, Actin, Desmin, CD 34, S 100 protein, Ki 67, PCNA. The tumor cells were Vimentin and CD 10 diffuse positive, focal Actin positive, Desmin, KL 1, CD 34 and S 100 protein-negative. 85% of the tumor cells were PCNA positive and 25 % were Ki 67 positive. We conclude that undifferentiated endometrial sarcoma may express specific markers but also muscle-related antigens. These findings reflect a common relationship of the endometrial stromal cells to the myometrium. Knowledge of these immunoreactivity patterns is essential when evaluating poorly differentiated uterine endometrial sarcoma .It simulates morphological pattern of muscle uterine tumors.