A previously healthy 34-year-old woman was admitted to our hospital with acute epigastric pain, a palpable abdominal mass, nausea, and weight loss of 2 kg in the last 2 weeks. Physical examination findings disclosed that the patient weighed 51 kg and was 170 cm tall, and was in good general health, with right upper quadrant tenderness, slight peritoneal symptoms, a nondistended abdomen, and normal bowel sounds. Body temperature was 38.2°C. The leukocyte count was slightly elevated at 9.8 × 109/L (reference, < 9.5 × 109/L), and C-reactive protein level was 18 mg/L (reference, < 5 mg/L) (to convert to nanomoles per liter, multiply by 9.524). A chest radiograph yielded normal findings. Abdominal sonography revealed a cystic lesion 8 × 4 cm in greatest diameter next to a small gallbladder, without other intra-abdominal pathologic findings. Subsequent magnetic resonance cholangiopancreatography confirmed the cystic lesion (Figure 1). Laparotomy revealed a cystic tumor 8 cm in greatest diameter at the lateral border of the hepatoduodenal ligament (Figure 2).