Ultrasound evaluation of schwannoma of the hand and wrist: case series analysis and literature review

Schwannoma is the most common benign tumor of peripheral nerves but represents only 5-8% of all soft tissue tumors, with the incidence of schwannoma of the hand and wrist reported as low as 1%. The ultrasound exam is the first imaging to approach to a clinically palpable swelling. We present a case series where the diagnosis of schwannoma is made on the basis of sonographic features. Schwannoma usually presents as a homogenous, hypoechoic mass, with internal vascular signal at color-Doppler, with posterior acoustic enhancement, pseudo-cystic appearance and target appearance. The nerve-tumor position is eccentric and nerve-tumor transition was clearly defined. These features allow us a correct diagnosis and a correct surgical planning. In fact, when the diagnosis of schwannoma is made a microsurgical technique is chosen, with nerve sparing and restitution ad integrum.