Glomus tumor cells: evaluation of smooth muscle and endothelial cell properties

Six cases of glomus tumor in superficial soft tissues were investigated immunohistochemically for the presence of different types of intermediate filaments, myosin, laminin, a basal lamina glycoprotein, and the endothelial cell markers, factor VIII-related antigen (FVIIIR:Ag) and Ulex europaeus I lectin (UEA I) binding sites. The tumor cells appeared to contain only vimentin, the fibroblast-type of intermediate filament protein. They were also positive for myosin, and were invested by laminin-positive basal lamina-like material, but did not express endothelial cell markers. Ultrastructural studies revealed prominent arrays of both intermediate filaments and microfilaments, the latter resembling the myofilament bundles seen in smooth muscle cells. The results show that glomus tumor cells resemble smooth muscle cells in their content of myosin and in some ultrastructural features. In their lack of desmin, however, they differ from most types of smooth muscle cell, although they are similar in this respect to some vascular smooth muscle cells.