Endometrial cancer is primarily associated with postmenopausal women. However, endometrial cancer associated with pregnancy is uncommon. Total abdominal hysterectomy and bilateral salpingoophorectomy are the primary operative procedures for endometrial cancer. The conservative treatment by progestin therapy could be considered to who wished to preserve the childbearing ability. We report a case about a 26-year-old women with focal well differentiated endometrial adenocarcinoma, and she was treated with progestin therapy (megesterol acetate) for 12 months. Thereafter, she was diagnosed with missed abortion and underwent a dilatation and curettage. Pathological examination of the tissue included chorionic villi and focal well differentiated endometrial adeocarcinoma. We have experienced the coexistence of endometrial adenocarcinoma and pregnancy.