Abstract
We herein report a very rare case of spontaneous regression of recurrent undifferentiated carcinoma of the endometrium. An 80-year-old woman had undergone total hysterectomy with bilateral adnexectomy for undifferentiated carcinoma of the endometrium. The cancer recurred locally 10 months after surgery and then metastasized to the lung and liver. After she and her family elected to receive supportive care without active treatment, the local recurrences dramatically decreased, and the metastases of the lung, liver, and peritoneum also disappeared. This case showed that spontaneous regression can occur even with malignant tumors showing an extremely poor prognosis, such as undifferentiated carcinoma of the endometrium.