Ultrasonographic and Clinical Characteristics of Schwannoma of the Hand

Abstract

Background: The purpose of this study was to report the ultrasonographic findings and clinical features of schwannoma of the hand.

Methods: We enrolled 8 patients who were initially diagnosed with ganglion by ultrasonography but finally with schwannoma by a tissue biopsy. We retrospectively analyzed the ultrasonographic findings of eight patients including echogenicity, internal homogeneity, posterior enhancement, internal vascularity, and clinical manifestations such as the occurrence site, tenderness, Tinel's sign, and paresthesia before the surgery.

Results: The occurrence sites were as follows: two cases on the thenar area, one case on the second web space, three cases on the third web space, one case on the radiovolar aspect of the proximal phalanx of the index finger, and one case on the radiovolar aspect of the proximal phalanx of the middle finger. Four patients suffered from tenderness and pain on presentation, and all patients had pain around the mass before presentation. Tinel's sign was present without paresthesia in one case. Ultrasonography revealed cystic lesions showing clear margins in all cases, and two of them had acoustic enhancement without internal flow.

Conclusions: It may not be easy to diagnosis schwannoma of the hand with ultrasonography alone when the lesion is small because of the similarity to the ultrasonographic findings of ganglion. Therefore, it is necessary to consider the possibility of schwannoma if a mass near the digital nerve or cutaneous nerve branch is accompanied by dull pain and tenderness.

Keywords: Hand; Schwannoma; Ultrasonography.

Fig. 1. The occurrence sites of schwannoma in the hand. The circled number indicates the number of occurrences.

Fig. 2. Ultrasonographic findings. Axial scan shows homogenous, anechoic round mass (arrow head) with posterior enhancement (asterisk) and flexor tendon of finger (arrow).

Fig. 3. Intraoperative photographs. (A) The yellowish-white colored ovoid mass (black arrow) was identified in the nerve at the bifurcation between the common digital nerve of the long and the ring fingers. (B) The yellowish-white colored solitary mass was enucleated microscopically. The white arrow indicates the digital nerve.

Fig. 4. Ultrasonographic features of ganglion and schwannoma. Schwannoma is often hypoechoic with posterior acoustic enhancement and thus may simulate a ganglion cyst. The diagnostic clue of schwannoma is nerve continuity.