65-year-old woman with finger mass
A glomus body is a component of the dermis layer of skin that is involved in temperature regulation. It consists of an arteriovenous shunt surrounded by a capsule of connective tissue. Glomus bodies are present most numerously in fingers and toes. Their function is to shunt blood away from skin when exposed to cold and allow maximum heat flow to skin in warm weather.
A glomus tumor is a rare, benign tumor that can arise anywhere in the body but shows a predilection for distal extremities, especially under the nail bed. Glomus tumors are mesenchymal neoplasms composed of cells resembling the modified smooth muscle cells of a normal glomus body.
Glomus tumors consists of less than 2% of soft tissue tumors. Multiple lesions may be seen in 10% of patients. Most are diagnosed in young adults but may occur at any age. Glomus tumors occur with equal frequency in men and women, except for subungal lesions, which are far more common in women. Fewer than 40 malignant glomus tumors have been reported in literature.
Multiple familial glomus tumors show autosomal dominant inheritance. These tumors are caused by inactivating mutations in the GLMN gene, which is located on chromosome 1.
Histologically, sheets and nests of uniform, round to epithelioid cells arranged around blood vessels are seen. Glomus cells are small, uniform, and rounded with a centrally placed, round nucleus and amphophilic to lightly eosinophilic cytoplasm. Each cell is surrounded by a sharply defined basal lamina. The stroma may show hyalinization or myxoid change. The tumor cells are positive for smooth muscle actin (SMA) and caldesmon and negative for desmin, S100, cytokeratins, and neuroendocrine markers like synaptophysin.