Dermoid cyst with secretion of CA 19-9 detected by (18)F-FDG PET/CT: A case report

INTRODUCTION: Carbohydrate antigen 19-9 (CA 19-9) is a tumor glycolipid, frequently elevated in the serum of patients due to malignancies from gastrointestinal organs; in particular, the pancreas. This carbohydrate antigen is also expressed in benign diseases. PATIENT CONCERNS: A case of a 27-year-old female who has an unknown origin CA 19-9 elevation for 2 years. DIAGNOSIS: After the left ovarian cystectomy and microscopic examination, the final diagnosis is a dermoid cyst. The dermoid cyst shows increased (18)F-fluorodeoxyglucose ((18)F-FDG) uptake in the (18)F-FDG positron emission tomography (PET)/computed tomography (CT) study. INTERVENTION AND OUTCOMES: The laparoscopic oophorocystectomy was performed. It was observed that the patient's CA 19-9 level returned to normal after the surgery 6 months later. This showed that the dermoid cyst was responsible for the abnormal CA 19-9 level. CONCLUSION: In this case, we can learn that the (18)F-FDG PET/CT scan has potential use in patients with unknown origin of elevation CA 19-9.