The finding of a glomus tumour in sites so unusual, as in the case we describe, may requires distinction from other tumours including haemangiopericytoma because of the arrangement of tumour cells around the many branching vessels. However glomus cells are generally closely packed and more consistently round or polygonal. Immunocytochemical analysis resolves the differential diagnosis because the glomus cells contain considerable amounts of smooth muscle myofilaments that give positive immunostaining for smooth-muscle actin. Haemangiopericytoma cells rarely contain myofilaments and actin immunoreactivity is seen in only rare cases and, when present, is usually focal and weak. Another lesion that might be considered in the histological differential diagnosis is glomangiopericytoma characterized by histological features that are intermediate between glomus tumour and haemangiopericytoma such as prominent branching, medium and small vessels lined by a single row of endothelial cells, surrounded by epithelioid cells with a glomoid appearance.