Imaging description

A subungual glomus tumor is usually not visible on radiographs unless it is causing erosion of the dorsal surface of the distal phalanx (Figure 42.1). This is readily differentiated from exostosis, which is seen as an osseous protuberance rather than an erosion (Figure 42.2). MRI has visualized subungual glomus tumors as small as 2 mm in size. The classic MRI appearance is iso- or hypointense on T1-weighted images, hyperintense on T2-weighted images, and strong enhancement with IV contrast.

Importance

Subungual glomus tumors need to be preoperatively identified. Subungual glomus tumors can be suspected by their characteristic clinical manifestation. However, because glomus tumors cannot be detected by visual inspection or palpation, they are sometimes diagnosed wrongly. Even if the clinical diagnosis is correct, surgery without knowing the exact size and location of the glomus tumor may result in incomplete excision, and thus recurrence. It is possible that no tumor is found by surgery leading to unnecessary deformity of the nail bed and finger. The combination of the correct clinical manifestation and MRI appearance is helpful in preventing unwarranted or unsuccessful surgeries.