Glomus tumors

General: Arise from modified smooth muscle cells of a "glomus body" (a specialized arteriovenous anastomosis involved in thermoregulation). Typically found under fingernails, but also anywhere in the skin, the flexor surface of the elbow or knee, and the GI tract.

Gross: Usually <1cm, rounded, red-blue, and firm.

Microscopic: Branching vascular channels separated by stroma containing nests of glomus cells, which are small, regular, round, with indistinct nucleoli. May be more infiltrative in children. May have myxoid change.

• Glomangioma: Resemble cavernous hemangioma.
• Glomangiomatosis: Resembles angiomatosis with excess glomus cells and fat, often associated with pain.

Differential Diagnosis:

Stains:

• Positive: SMA, vimentin
• Negative: CKC, desmin
• Suggested, focused panel:

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Cases:

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