Endothelium in hepatic cavernous hemangiomas does not express the hyaluronan receptor for endocytosis.

The liver contains two distinct endothelial cell types: vascular and sinusoidal. Although cavernous hemangioma is the most common benign tumor of the liver, vascular or sinusoidal endothelial cell differentiation has not been described. An endocytic receptor responsible for the uptake and degradation of hyaluronan is present in the sinusoidal endothelium of the liver. The hyaluronan receptor for endocytosis (HARE) may therefore be a useful marker for sinusoidal endothelial cell differentiation. Using monoclonal antibodies specific for HARE, CD31, and factor VIII, we completed an immunohistochemical study of the endothelial cells of both hepatic cavernous hemangiomas and of nonneoplastic human liver. The anti-HARE monoclonal antibodies showed diffuse strong staining of nonneoplastic liver sinusoidal endothelium. No staining of nonsinusoidal endothelium or the endothelial lining of the hemangiomas was seen with anti-HARE. In contrast, diffuse strong staining for factor VIII and CD31 was present in nonsinusoidal endothelium and cavernous hemangioma endothelium. Neither factor VIII nor CD31 staining was present in the sinusoidal endothelium. In conclusion, the endothelium of hepatic cavernous hemangiomas demonstrates vascular but not sinusoidal differentiation based on the absence of HARE and presence of CD31 and factor VIII.