Hepatic mesenchymal hamartoma showing hepatobiliary-phase signal increase on gadoxetate disodium-enhanced magnetic resonance imaging: A case report.

We report a case of a 9-month-old girl with mesenchymal hamartoma that was evaluated using gadoxetate disodium-enhanced magnetic resonance imaging. Imaging revealed a large hepatic mass with mixed cystic and solid components, with a slight signal increase in the solid component during the hepatobiliary phase. Histopathology confirmed mesenchymal hamartoma, with normal hepatic parenchyma reticularly interspersed within the mass. Immunohistochemical staining for organic anion transporting polypeptide 1B3 showed cytoplasmic immunoreactivity without membranous staining in hepatocyte-like cells. Mesenchymal hamartoma is a rare benign liver tumor in children, accounting for approximately 8% of all pediatric hepatic tumors. This case suggests that mesenchymal hamartoma may show a slight hepatobiliary-phase signal increase, potentially reflecting delayed contrast retention within the interstitium of the solid component.