ABSTRACT
A 61-year old woman underwent total abdominal hysterectomy and pelvic lymph node dissection under the diagnosis of endometrial cancer. Although pelvic lymph nodes were positive for adenocarcinoma with psamomma bodies, no other lesion that was a primary lesion was verified. A postoperative study revealed the existence of para-aortic lymph node and supraclavicular lymph node metastases. Therefore, the endometrial biopsy specimen was reviewed. With the findings of p53 positivity by immunohistochemistry in the papillary part, the final histopathological diagnosis was changed to endometrial serous adenocarcinoma. Postoperative chemotherapy followed by radiotherapy for supraclavicular lymph node metastasis achieved complete response. This type of tumor must be considered in a differential diagnosis when metastatic papillary serous carcinoma is detected, but the primary site remains unknown.