On lateral radiograph of the fourth digit of the left hand, an obvious thinning of the dorsal cortical bone at the tip of the distal phalanx is seen (arrow).
MRI of the fourth digit of the left hand included sagittal SE T1-weighted image, sagittal SE T2-weighted image, axial SE T1-weighted image and Gd-enhanced axial SE T1-weighted image.
The sagittal and axial MR images demonstrate a small ovoid soft-tissue mass located at the posterior border of the distal phalanx. The mass is isointense with muscle on T1-weighted images and hyperintense on T2-weighted images. There is a marked enhancement after Gadolinium administration. Note also the erosion of the dorsal cortical bone.
Pathohistologic examination after resection revealed a benign glomus tumor.
Soft tissue glomus tumors with secondary osseous involvement are characteristically located in the distal phalanx of the hand. Occasionally the proximal and middle phalanx can be involved. Presence of multiple glomus tumors occurring in one digit has been described.
On conventional films, the tumor produces thinning or well marginated erosions of the adjacent bone, usually at the terminal phalanx. Sometimes, a sclerotic margin may be present surrounding the erosion. Because the lesion is richly vascularized, it shows a marked contrast enhancement on MR images after intravenous injection of Gadolinium. The differential diagnosis includes epithelial inclusion cyst, hemangioma and mucoid cyst. The latter shows similar MR characteristics as glomus tumor, but does not enhance after contrast injection.
 Dalrymple NC, Hayes J, Bessinger VJ et al. MRI of multiple glomus tumors of the finger. Skeletal Radiol 1997; 26: 664-666.
 Drape JL, Peretti I, Goettmann S et al. Subungual glomus tumors: evaluation with MR imaging. Radiology 1995; 195: 507-515.
 Kalisher L. Epidermoid inclusion cyst of the phalanx, radiological and clinical correlation. Rev Interam Radiology 1997; 2: 47-48.