The levonorgestrel-releasing intrauterine system (LNG-IUS) is used for contraception and treatment of heavy menstrual bleeding as well as endometrial hyperplasia and early endometrial carcinoma. A 48-year-old woman visited an Internal Medicine outpatient clinic due to significantly elevated CA-125 and CA-19-9 levels in a routine health examination. She had been using LNG-IUS for 3 years. Before LNG-IUS insertion, she suffered from heavy menstrual bleeding and severe dysmenorrhea. Her endometrial sampling and ultrasonographic imaging showed no evidence of endometrial carcinoma at the time of LNS-IUS insertion. After insertion, she complained of neither abnormal uterine bleeding nor dysmenorrhea. She received a routine health check-up every year and showed results within normal range until last year. To rule out pancreatic cancer due to significantly elevated CA-19-9 levels, her physician performed positron emission tomography–computed tomography, which demonstrated increased FDG uptake in the endometrial cavity. We obtained endometrial biopsy and found endometrial carcinoma in her uterus and performed radical hysterectomy with bilteral pelvic lymphadectomy. Permanent pathology confirmed endometrial carcinoma with lymph node metastasis. She received concurrent chemoradiation therapy. We emphasize the necessity of regular follow-ups with ultrasonography and assessment of serum tumor markers for the early detection of endometrial carcinoma, although rare, in women using LNG-IUS, including those without abnormal uterine bleeding.

Introduction
 Case report
 Discussion
 Acknowledgements
 ORCID
 References

• Oh-Young Lee(Department of obstetrics and gynecology, Chungbuk National University Hospital)
• Young-Ok Shin(Department of obstetrics and gynecology, Chungbuk National University Hospital)
• Eugene Kim(Department of obstetrics and gynecology, Chungbuk National University Hospital)
• Eun-Hwan Jeong(Department of obstetrics and gynecology, Chungbuk National University Hospital, Chungbuk National University College of Medicine, Cheongju 362-711, Korea)