The molecular biology of hemangioendothelioma is largely uncharacterized, although VEGF expression and abnormalities in the p53 tumor suppressor pathway have been shown to be associated with less-differentiated (defined by a lack of endothelial-specific storage granules known as Weibel-Palade bodies) tumor regions in a patient with metastatic disease (Theurillat et al., 2003). The gene discussed is TP53; the disease is neoplasm.