Early endometrial cancer shows only a slight thickening of the endometrium, which cannot be differentiated from endometrial hyperplasia, and therefore is difficult to diagnose by ultrasound, and needs to be diagnosed on the basis of history and diagnostic scraping. Therefore, it is difficult to be diagnosed by ultrasonography, and it needs to be diagnosed according to the history and diagnostic scraping. Therefore, it is difficult to detect many endometrial cancers in early stage by ultrasonography. Moreover, the chances of detecting early endometrial cancer by abdominal ultrasonography are relatively low compared to negative ultrasonography. This is because ultrasound shows less clarity. Moreover, endometrial cancer is categorized into two types: limited type and diffuse type. If it is limited type endometrial cancer, the lesion is relatively small in the early stage, and some of them only show a little thickening of the endometrium, and there is no obvious abnormal clinical symptom, so it is not easy to distinguish it from endometrial hyperplasia under ultrasound. In addition, if it is diffuse endometrial cancer, i.e. the endometrium mainly involves the whole uterine cavity, it is difficult to be diagnosed by ultrasound in the early stage, and it needs to be combined with diagnostic scraping and pathologic examination. As the disease progresses, endometrial thickening, focal or diffuse uneven mixed echoes, or lesions involving the myometrium or cervix can be detected by ultrasonography. Therefore, ultrasonography is still difficult to diagnose early endometrial cancer. For middle and late endometrial cancer, a more accurate diagnosis can be made according to the ultrasound performance. Transvaginal ultrasonography is also more accurate in determining the depth of myometrial infiltration of endometrial cancer and the involvement of the cervix. Therefore, when abnormalities are found or there is a tendency of endometrial cancer, further hysteroscopy and pathology can be recommended to confirm the diagnosis.