Glomus tumours arise from the arterial portion of the glomus body, or the Sucquet-Hoyer canal. The glomus body is a temperature-sensitive organ of modified perivascular smooth muscle cells, which is involved in the vascular regulation of skin temperature; arterioles contract with cold whereas glomus bodies dilate, thereby maintaining blood flow to the nail bed.
Classification of glomus tumours
Glomus tumours have previously been classified into solitary, multiple and congenital, or histologically by the prevailing cell type into glomus tumours (predominant cell – glomus cells), glomangiomas (blood vessels) and glomangiomyomas (smooth muscle cells). However, glomangiomas are now probably best considered as a subtype of venous malformation, rather than as a tumour.
Glomus tumours are typically a solitary, painful 1-2 cm reddish blue papule or nodule found on a young adult. They most commonly affect the nail bed or the palm. They are usually tender to touch, but may be extremely painful, particularly following change in temperature or pressure.
Extracutaneous glomus tumours have been reported rarely in the gastrointestinal tract, mediastinum, trachea, mesentery, cervix and vagina.
Under the microscope (histologically), there are solid sheets of glomus cells around small blood vessels. Immunohistochemical studies may be helpful in diagnosis.
© Dr Ph Abimelec – dermatologue
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Glomangiomas or glomuvenous malformations
Glomangiomas, on the other hand, are less common glomuvenous malformations, and are typically found in infancy or childhood. They have been reported at birth (congenital), although rarely. They are usually multiple, soft, red-to-blue nodules but may appear as pink to deep blue plaque-like lesions. They are often widespread, and can join together to become larger plaques. They tend to get thicker and bluer with age. Although they start off painless, they may become tender to touch.
Under the microscope (histologically) they resemble venous malformations with large, dilated, thin-walled veins in the dermis and subcutaneous tissue, but have clusters of α-actin-positive glomus cells lining the venous spaces. They are less circumscribed than glomus tumours.
Although most glomuvenous malformations are sporadic, there are a number of reports of segmental multiple glomus tumours with an autosomal dominant pattern of inheritance (this is where ½ the children of an affected parent will inherit the condition). An abnormal chromosome 1p21–p22 has been identified in these families. It is associated with damage to a protein called glomulin.
Solitary glomus tumours can be surgically excised but this becomes difficult with multiple glomuvenous malformations. Other treatment options include laser, injection with hypertonic saline and sclerotherapy.