Intravascular papillary endothelial hyperplasia arising from the upper lip.

We report a rare case of intravascular papillary endothelial hyperplasia (IPEH) arising from the upper lip. Pathologically, it consisted of a few lobulated masses lined by an incomplete fibrous capsule of variable thickness which was separated from the surrounding tissue and which partially formed papillary structures bearing fibrous stalks and a single layer of endothelium. The capillary formation was poorly defined, and mitotic figures were frequently observed. Immunohistochemically, the endothelial cells were positive for factor VIII related antigen and vimentin, and many cells were positive for PCNA, not only in the solid proliferating area but also in the papillary proliferating area. This case represents IPEH with high proliferative activity.