Multifocal glomus tumours of the fingers in two patients with neurofibromatosis type 1.

Aglomus tumour of the finger is a benign tumour that develops from the neuromyoarterial elements of the glomus body, which is a specialised arteriovenous anastomosis involved in thermoregulation. In this structure the arterioles that connect with venules have a thick layer of concentrically arranged epitheloid smooth muscle cells. Contraction of the layer of smooth muscle cells results in closure of the arteriovenous anastomosis and this will force blood to flow through the capillary network. Control of the function of the arteriovenous anastomoses is mainly neural. Most glomus tumours are localised in the distal phalanx. It is a small tumour with a subungual or pulpar localisation and with typical symptoms consisting of the triad pain, cold intolerance, and very localised tenderness. Most cases of phalangeal glomus tumours are solitary. A related condition called multiple glomuvenous malformations of the skin shows autosomal dominant inheritance and is linked to the chromosome 1p21-22 region. The abnormalities in the skin consist of cutaneous venous malformations with smooth muscle-like glomus cells. Recently the gene involved in this familial condition has been cloned and named glomulin. Glomuvenous malformations of the skin are clinically and aetiologically different from the sporadic glomus tumours of the distal phalanx. The jugular glomus tumours seen in familial paragangliomas originate in a structure of a different type from the glomus bodies of the fingers. The carotid and jugular bodies have a different histology; most are chemoreceptors and they consist of a spherical conglomeration of cells and small blood vessels. Therefore, they are also called glomera. The association of glomus tumours of the fingers with neurofibromatosis type 1 (NF1) is rarely observed with only 12 cases having been reported previously.