An Extradigital Glomus Tumor in the Upper Arm

Abstract

A glomus tumor is a rare vascular neoplasm arising from the glomus body and the most common site is hand, especially subungual region of the finger and palm. A 68-year-old male with medical history of colon cancer with liver metastasis came to our clinic complaining of a solitary painful erythematous papule on his right upper arm for about one month. The patient had no history of trauma. Physical examination revealed a 0.7cm-sized, dome-shaped, painful erythematous papule with significant tenderness on posterior aspect of right upper arm. We performed punch biopsy under the impression of cutaneous metastasis of the cancer or hypertrophic scar. Skin biopsy showed varying proportions of glomus cells, blood vessels, and smooth muscle, and monomorphic round cells with eosinophilic cytoplasm. Immunohistochemistry stain was positive for smooth-muscle actin (SMA), whereas S100 and HMB45 were negative, confirming the diagnosis of solid type of glomus tumor. The lesion was removed from the biopsy, and there was no evidence of recurrence after 10 months of follow-up. We herein report a rare case of extradigital glomus tumor on the upper arm which is occasionally difficult to diagnose before histological and immunohistochemical confirmation.