Glomus Tumor

Glomus tumor is a rare and benign vascular tumor. The normal glomus unit is a neuromyoarterial apparatus that functions to regulate skin circulation and is found subungually, on the finger tip pulp, on the base of the foot and the rest of body in descending order. The most common site of glomus tumors is subungual and 75% of the lesions occur in the hand.

Other sites include the palm, wrist, forearm and foot. Glomus tumor can occur near the tip of the spine, where it may arise from the glomus coccygeum. Glomus tumors have also been described in locations where the glomus body does not normally occur. Unusual sites include the patella, bone, chest wall, eyelid, colon, rectum, cervix, and other sites. Glomus tumors rarely arise directly from bone.

The lesions present most frequently during the fourth and fifth decade of life although they can be found in any age and at any site. The subungual tumors affect women three times more commonly than men. The lesions are usually solitay but several reports of mulifocal tumors have been published.

Clinically, glomus tumors are characterized by a triad of sensitivity to cold, localized tenderness and severe intermittent pain. The pain can be excruciating and is described as a burning or bursting.The exact cause of the pain is not completely understood, but nerve fibers containing the pain neurotransmitter substance P have been identified in the tumor.

Grossly, the tumors are usually less than one cm. in size, and appear as small red-blue nodulas. The lesion appears as a localized dark red or blue lesion beneath the finger nail, but the subungual lesions can be difficult to detect on clinical examination. Radiographs of the distal phalanx show a small scalloped osteolytic defect with a sclerotic border.

Radiologically, glomus tumors appear as well circumscribed osteolytic lesions. The lesion shows either bone erosion or invasion depending on where it arises. A sclerotic border is present due to the slowly enlarging
mass. CT scan shows a non-specific subungual mass. T1 MRI is not as useful for subungual lesions as it only demonstrates a dark, well delineated mass. Glomus tumors appear as a very high and homogeneous signal intensity on T2 weighted images. MRI is useful for the detection of lesions in the soft tissues. The radiological differential includes epidermal inclusion cyst, enchondroma, chronic osteomyelitis, sarcoidosis, metastatic carcinoma, subungual melanoma and osteoid osteoma.

Under the microscope, glomus tumors are found at the dermal and subdermal junction and have a fibrous capsule. They are made of an afferent arteriole, anastomotic vessel, and collecting venule. These vascular
structures are surrounded by rounded uniform epithelioid cells with granular cytoplasm known as glomus cells or pericytes. Also present are smooth muscle cells and non-myelinated nerve cells. There is no pleomorphism or
mitotic activity. There are three forms of glomus tumors: vascular, myxoid and solid. The vascular form consists of mostly vessels with little epithelioid component. The solid form has sheets of glomus cells with few vessels. Glomus tumors stain positive for the smooth muscle marker actin.

Treatment of glomus tumors consists of surgical excision. Repair of the nail bed must be performed after the removal of subungual lesions. Relief of pain is usually intermediate after surgery.

References
Johnson, DL et al., Intraosseous Glomus Tumor of the Phalanx: A Case Report, Journal of Hand Surgery (American):18(6):1026-8, November, 1993.

Kishimoto S et al., Immunohistochemical demonstration of Substance-P containing nerve fibers in glomus tumors. Br J Dermatol 113:213, 1985.

Murphey, MD et al., Musculoskeletal Angiomatous Lesions: Radiologic-Pathologic Correlation, Radiographic, 15:893917, July, 1995.

Takei, TR and EA Nalebuff, Extradigital Glomlis Tumor, Journal of Hand Surgery (British), 20B(3):409-412, June, 1995.

Sunderraj, S et al., Primary Intra-Osseous Glomus Tumor, Histopathology, 14(5):532-536, May, 1989.

Heys, SD et al., Glomus Tumor: An Analysis of 43 Patients and Review of the Literature, British Journal of Surgery, 79:345-347, April, 1992.

Vandevender, DK and RA Daley, Benign and Malignant Vascular Tumors of the Upper Extremity, Hand Clinics, 11 (2): 161 - 179, May, 1995.

Huvos, Andrew, Bone Tumors Diaonosis. Treatment and Prognosis, W.B. Saunders, Co., 1991.

1/22/98 revised 8/20/01 HD