Thyroid mass from a malignant glomus tumor: Case report and literature review

Objectives Glomus tumors arise in the dermal glomus body and are most commonly found in the subungual region of the digits, the dermis or the subcutis of the palm, wrist, forearm or foot. They are typically benign and localized but rare cases of malignant glomus tumor have been described. Here, we describe the first reported case of glomus tumor metastasizing to the thyroid gland. Study design Case report and literature review. Methods A 40-year old male with a history of glomus tumor of the dorsal aspect of his left foot status-post wide local excision with metastatic disease that was well controlled for four years with chemotherapy and radiation presents with a slowly enlarging left thyroid mass. The mass was first identified on surveillance CT and enlarged from 1.3 cm to 2.4 cm over the course of six months. Fine-needle aspiration of the mass demonstrated atypical epitheliod cells with conspicuous nuclei and scatter mitosis with immunostains positive for SMA, focally positive for calponin and negative for PAX-8 consistent with metastatic malignant glomus tumor. Results The patient underwent total thyroidectomy and final pathology was consistent with metastatic glomus tumor. Conclusion This is the first reported case of a glomus tumor metastasizing to the thyroid gland. This case illustrates several important points for otolaryngologists and highlights the differences between glomus tumors and paragangliomas, which were formerly also called glomus tumors. Although rare, malignant glomus tumors are an additional entity to consider when assessing a patient with an unusual appearing thyroid mass.