Intravascular glomus tumour: a previously undescribed phenomenon.

We report the first case of an intravascular glomus tumour, which was located in the right forearm of a 40-year-old male. Microscopically the lesion originated from the wall of a vein and protruded into the lumen of the affected blood vessel. The tumour cells were characterized immunohistochemically by the presence of vimentin, actin and myosin. Within the tumour, small nerves, immunopositive for S-100 protein and neurofilaments, could be identified. Histogenetically, the tumour is thought to derive from intramural epithelioid cells of the venous part of an arteriovenous anastomosis.