Background: Smoothelin is a specific marker for smooth muscle cells with contractile capacity which has not been widely studied in glomus lesions. In the same way, the expression for Wilms tumor 1 (WT1) has only been studied occasionally in the endothelial cells of glomovenous malformations and in the glomus cells of glomus tumours.
Objective: We studied the significance of immunohistochemical expression of smoothelin and WT1 in 25 glomus lesions.
Methods: We assessed 9 cases of solid glomus tumors (SGT), 8 cases of glomus tumors with vascular ectasia (VEGT), 2 cases of glomangiomyomas (GMM) and 6 cases of glomuvenous malformation (GM). Immunohistochemistry was performed, evaluating the expression of WT1, smoothelin, smooth muscle actin (SMA), smooth muscle myosin (SMM), h-caldesmon and desmin.
Results: Glomic cells showed cytoplasmic positivity for smoothelin, and WT1 expression was present in all studied cases. SGT showed WT1 positivity in all endothelia. However, in regarding VEGT and GMM, WT1 endothelial expression was positive in some areas, but not in others. GM did not show endothelial cell positivity for WT1.
Conclusions: Smoothelin expression in glomic cells indicates that they are contractile smooth muscle cells, and thus its role in routine diagnosis should be considered. The absence of WT1 expression in the endothelium of the vascular structures of the GM is a differential characteristic between SGT, VEGT and GMM.