Endothelial cell differentiation in hepatocellular adenomas: implications for histopathological diagnosis

Little information is available about the patterns of endothelial cell differentiation observed in hepatocellular adenomas. We therefore aimed to analyze the endothelial cell immunophenotype in a large series of these tumors and evaluate its possible diagnostic relevance.

The expression of continuous and sinusoidal endothelial cell markers and of extracellular matrix proteins was analyzed by immunoperoxidase in 56 adenomas, as compared with 30 cases of focal nodular hyperplasia (FNH), 2 cases of telangiectatic FNH and 40 cases of hepatocellular carcinoma (HCC).

Twenty-eight adenomas (50%) presented a sinusoidal pattern of endothelial cell differentiation, characterized by the expression of specific sinusoidal endothelial cell markers and the presence of a subendothelial matrix resembling the normal perisinusoidal matrix. Eleven tumors (19.5%) presented a continuous pattern of endothelial cell differentiation. Seventeen tumors (30.5%) showed a mixed pattern. Twenty-eight FNH presented a sinusoidal pattern of endothelial cell differentiation; all HCC presented a continuous pattern of endothelial cell differentiation.

In hepatocellular adenomas, intra-tumoral vessels usually present a sinusoidal pattern of endothelial cell differentiation. However, the vascular phenotypic heterogeneity observed in our study questions the potential relevance of endothelial cell immunophenotyping for the differential diagnosis between hepatocellular adenomas and well differentiated HCC.