This 74-year-old woman presented with a painful lesion on her arm. The clinician submitted it as a possible neuroma or irritated nevus. Glomus tumors are derived from the temperature-regulatory smooth muscle apparatus designed to shunt blood. Therefore they are not endothelium-derived like most vascular tumors. Glomus and glomangioma can be used interchangably, often reflecting the relative amount of cellular and vascular components. Glomus can be painful, as in this case, and is the "G" of the ANGEL mneumonic for painful cutaneous neoplasms.
High power clearly demonstrates the bland uniformity of the neoplastic cells in a perivascular distribution. They are low-cuboidal with well-defined eosinophilic cytoplasm. Mitoses and atypia are not present.