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Intraductal oncocytic papillary neoplasm: a benign hepatic cystic neoplasm. A 61-year-old Asian man presented with severe right upper quadrant pain which had been worsening for several months. Laboratory results indicated elevated aspartate aminotransferase and alanine aminotransferase. The subsequent ultrasound, CT and MRI showed a large cystic mass with solid components and severe intrahepatic and extrahepatic biliary ductal dilatation. The mass was resected and pathology showed a well-demarcated mucinous cystic lesion with polygonal cells containing ovoid nuclei and abundant pink oncocytic cytoplasm. These findings are characteristic of intraductal oncocytic papillary neoplasm (IOPN), a rare subtype of intraductal papillary neoplasm of the liver. IOPN occurs most frequently in the Asian regions endemic to clonorchiasis and hepatolithiasis; however, cases have been reported in the Western world as well. Patients with IOPN are male or female and typically middle-aged. Treatment is typically resection. Prognosis is favourable and recurrence is rare. The 5-year survival rate is upwards of 80%.