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Clinique St. Pierre Ottignies B-1340, Belgium
Glomus tumor is a benign tumor (hamartoma) developing from the neuromyoarterial glomus bodies that regulate blood flow in the skin [1, 2]. Early occult lesions can sometimes present a diagnostic dilemma, and MR angiography can be diagnostic.
A 37-year-old woman presented with a 2-week history of point tenderness at the nail of the fourth finger of the left hand, with cold sensitivity. Radiographs showed no obvious abnormality at first but retrospectively revealed a subtle thinning of the dorsal cortical bone at the tip of the distal phalanx (Fig. 4A).
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High-resolution real-time sonography depicted a small hypoechogenic mass (Fig. 4B) but showed no modification on color or power Doppler sonography.
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MRI was performed on a 1-T unit; sequences available were coronal STIR
imaging, transverse proton density–weighted imaging with fat saturation,
3D contrast-enhanced MR angiography, and transverse T1-weighted fatsuppressed
imaging after IV contrast medium injection. Only the MR angiography
(Fig. 4C) depicted a small
ovoid blush. No enhancement appeared on the late delayed contrast-enhanced
sequence.
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Glomus tumor (glomic tumor, glomangioma) constitutes 1–5% of the soft-tissue tumors in the hand [2, 3]. The normal glomus (glomus body) is an arteriovenous shunt that is composed of an afferent arteriole, an anastomotic vessel (Sucquet-Hoyer canal), a collecting vein, and a capsular portion [2]. Histologic analysis shows vascular channels surrounded by irregularly arranged cuboidal cells. Nerves are found and may account for the pain. The tumor is surrounded by a fibrose capsule. Glomus tumor may be considered a hamartoma rather than a true tumor [3]. The tumor is most commonly found on the distal extremities (75% occur in the hand) in the nail bed and subcutaneous tissue, especially at the tips of the first to fourth fingers [1–3].
At physical examination, local soft-tissue tenderness and thickening may be apparent. Often symptoms have been present for several months or years, and nail plate avulsion could be a diagnostic aid. Sometimes the pain is worse at night; it may disappear when a tourniquet is applied. In our patient, pain was present for only 2 weeks and involved no specific coloration of the nail bed.
Lateral radiographs may show obvious thinning of the dorsal cortical bone of the distal phalanx, although this was barely visible in our patient.
High-resolution real-time color or power Doppler sonography is sensitive for tumors as small as 3 mm in diameter, but results are operator-dependent. Repetitive sonographic examination of our patient revealed a small questionable hypoechogenic nodule.
Because the glomus is richly vascularized, it shows marked contrast enhancement on MRI after IV injection of gadolinium [4]. Careful attention must be paid at the arterial or arteriovenous phase of imaging. Indeed, in some early glomus tumors, it is possible that only MR angiography can depict the lesion. We performed conventional MR angiography (the same as for a carotid study) with a circular polarized extremity coil and real-time triggering MR fluoroscopy of the target vasculature (Care Bolus, Siemens Medical Solutions, Erlangen, Germany). Parameters were as follows: TR/TE, 4.40/1.8; slice thickness, 0.8 mm; 80 slices per slap; field of view, 300 mm; and voxel size, 1.1 x 0.8 x 0.8 mm.
Other possible diagnoses include mucoid cyst, hemangioma, epithelial inclusion, and tendon giant cell tumor [4]. Treatment is by surgical excision, and MRI may be helpful before surgery to locate the tumor and ensure complete excision with removal of the capsule to prevent possible recurrence.
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