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WHO Classification of Tumours
Glomus tumor, NOS
Connective, subcutaneous and other soft tissues


Glomus tumours are rare mesenchymal neoplasms composed of cells that resemble the modified smooth muscle cells of the glomus body. The majority of glomus tumours occur in the distal extremities, particularly the subungual region, hand, wrist and foot. They arise in skin or superficial soft tissues; rare cases can also be found in deep soft tissue or viscera. Cutaneous lesions are usually small (<1 cm), red-blue nodules. The glomus cells making up the tumour are small, uniform, rounded cells surrounded by basal lamina. Depending on the relative proportion of glomus cells, vascular structures and smooth muscle, three subtypes of typical glomus tumours are distinguished:
> Solid glomus tumours (approximately 75% of cases) are composed of nests of glomus cells surrounding capillary sized vessels. Small cuffs of glomus cells are frequently observed around small vessels outside the main mass.
> Glomangiomas (approximately 20% of cases) are composed of small clusters
of glomus cells surrounding dilated veins.
> Glomangiomyomas are characterized by a transition from typical glomus cells to elongated cells resembling mature smooth muscle.
Glomus tumours typically affect young adults but may arise at any age. Subungual lesions show a distinct predilection for women; otherwise, the sexes are equally affected

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Fletcher CDM, Unni KK, Mertens F (Eds.)
World Health Organization Classification of Tumours. Pathology and Genetics of Tumours of Soft Tissue and Bone.
3rd Edition
IARC Press: Lyon 2002