A case of mucinous cystic neoplasm of the liver: description of Sonazoid-enhanced ultrasound imaging and histopathologic findings.

Mucinous cystic neoplasms (MCNs) of the hepatobiliary system are rare tumors that usually arise within the liver. We encountered a 63-year-old woman with a surgically proven MCN of the liver. We first performed contrast-enhanced ultrasound imaging, and the mass was found to have the appearance of a solid tumor, showing peripheral nodular enhancement in the arterial and portal phases with persistence of enhancement. The lesion remained enhanced in the post-vascular phase (Kupffer phase). Based on these findings, we incorrectly identified the tumor as a cavernous hemangioma, despite negative findings in computed tomography and magnetic resonance imaging. In our immunohistologic analysis using anti-CD68 antibody, the antibody-positive cells were identified as macrophages. Therefore, the Sonazoid microbubbles could have been retained within these macrophages, resulting in late enhancement. These findings appear to be of key importance in accurately diagnosing MCNs and clarifying their pathophysiology.