Glomus tumor of the lip. A case report and immunohistochemical study.

A rare glomus tumor of the lip is reported and--with nineteen glomus tumors from other sites--examined immunohistochemically with both monoclonal and polyclonal antibodies. In every case, the glomus cells showed strong reactivity with antivimentin, and factor VIII-related antigen was consistently identified in the endothelial cells but not in the glomus cells. Antiblood group A antigen was located in endothelial cells in nine cases; of these nine, five also showed focal staining in glomus cells. In no case was there reactivity with antibodies to common leukocyte antigen or cytokeratin proteins. These results support the hypothesis of Tajima et al. that the glomus cell is transitional--between smooth muscle and vascular endothelium--being essentially a modified, smooth muscle cell with some endothelial cell properties.