Infantile hemangioendothelioma of the liver in a neonate. Immunohistochemical observations.

The study documents the immunohistochemical features of a case of infantile hemangioendothelioma (IHE) of the liver, which was found incidentally at autopsy in a 44-day-old girl. A precardial apical systolic murmur and hepatomegaly were found on day 4 of life. The tumor was multifocal and histologically composed of vascular channels lined by endothelial cells that were positive for von Willebrand factor, CD31, vimentin, and Ulex europaeus agglutinin 1, and that were invested in a continuous basement membrane (BM) on the antiluminal border. The endothelial cells, especially in the region of intravascular buds, showed intracytoplasmic synthesis of BM components (laminin and collagen IV). Underlying the endothelial cells were cells with cytoplasm that was positive for alpha-smooth muscle actin and antimuscle actin and negative for desmin, and that were enveloped with BM. The immunophenotype, appearance, and location of these cells are characteristic of pericytes. We found neither signs of endocrine secretion nor hepatitis B virus in the tumor tissue. The appearance of this tumor in the neonatal period supports a fetal origin of IHE.