[Ultrastructure of eruptive capillary hemangioma (granuloma pyogenicum sive teleangiectaticum)]

Twelve lesions of so-called granuloma pyogenicum of the skin were examined by electron microscopy. The process is initially characterized by a solid proliferation of endothelial cells. The lumen is formed by a distention of the intercellular space and by invaginations of the cytoplasmic membrane. Even the walls of greatly ectatic vessels are only lined by endothelial cells, which is an indication for their capillary nature. Weibel-Palade bodies are rare. The basal lamina is born in the process of lumen formation and flattening of the endothelial cells. Cytoplasmic blebs on endothelial cell surfaces represent aqueous compartments. Their appearance probably results from a lack of energy supply due to an insufficient microcirculation. Exulceration of the epifocal epidermis is definitely a secondary event and leads to direct contact of the capillary vascular tissue with living and nonliving agents in the environment. This induces a strong acute inflammatory response, which results in fibrin exudation and emigration of neutrophilic granulocytes. The lesion is a benign vascular tumour. Therefore the term "eruptive capillary hemangioma" is justified.