Background

Glomus tumors are benign hamartomas originating from the glomus body.^[1] The glomus body is a neuromyoarterial apparatus composed of vascular structures, nerve cells, and smooth muscle cells. It is found in the dermis throughout the body, with the highest concentrations being in the hands and feet. The glomus body is responsible for thermoregulation.

Wood first described the clinical findings associated with glomus tumor in 1812. He presented cases of painful subcutaneous nodules that were characterized by pain and temperature sensitivity and that were curable with excision.^[2]

Pathophysiology and Etiology

In a glomus tumor, elements of the normal glomus body, vascular structures, nerve cells, and smooth-muscle cells are affected by marked hypertrophy, which leads to a nodulelike structure. The lesion sometimes appears as a locally enlarging mass. No evidence of mitosis is observed in the structure.

A few case reports have described glomus tumors possessing malignant potential.^{[3, 4]} Findings included the following:

• Large size
• Deep location
• Infiltrative growth
• Mitotic activity
• Nuclear pleomorphism
• Necrosis

Some reports mention metastases and death from the disease. Glomangiosarcoma is a rare malignant variant that may metastasize.

No risk factors for the formation of glomus tumors are known.

Epidemiology

Glomus tumors are rare. Congenital, familial, and multiple lesions are extremely rare.^[5]  The incidence of multiple tumors is 25%.^[6]

Glomus tumors are most commonly found in distal extremities in the nail bed and subcutaneous tissues of the distal phalanx. About 75% of glomus tumors occur in the hand, and 60% are subungual.^{[7, 8]} Other sites include the wrist, forearm, and foot,^[9] but the tumor can occur anywhere in the body. Glomus tumors have also been described at unusual sites, such as the patella, tendons, bone, eyelid, colon, rectum, kidney, and cervix.^[10] Intraosseous glomus tumors, which arise from bone, are similarly rare: Fewer than 20 cases of glomus tumor in bone have been reported in the literature.^{[11, 12, 13, 14, 15]}

Glomus tumors mostly occur in middle age, especially in the fourth and fifth decades of life. However, they have been described in all age groups. No clear sex predilection has been reported for glomus tumors in general; however, subungual glomus tumors appear to be more common in women than in men.

Prognosis

The outcome after complete excision with removal of the fibrous capsule is usually excellent, and pain relief occurs immediately after surgery. Recurrences are rare if the capsule is completely excised.