Diagnostic accuracy of multiparametric ultrasound for peripheral nerve schwannoma

Ultrasound (US) diagnostic techniques have the advantages of low cost, convenient operation, and high availability.

To explore the diagnostic accuracy of multiparametric US in evaluating signs of peripheral schwannoma.

This retrospective case-control study included patients with soft-tissue masses on the limbs (divided into the schwannoma and non-schwannoma groups) between January 2017 and November 2020. US features were compared between the two groups, and receiver operating characteristics analysis was used to evaluate the diagnostic efficacy of these features.

A total of 165 patients were included in this study; of them, 63 (38.2%) were diagnosed with schwannoma. Regular morphology (95.2% vs. 39.2%), cystic degeneration (71.4% vs. 27.5%), target sign on elastography (82.5% vs. 0), and polar blood supply sign (87.3% vs. 14.7%) were more common in schwannomas than in non-schwannoma lesions (all P < 0.001). Combining the four signs for diagnosis of schwannomas, the sensitivity, specificity, and accuracy were 95.24%, 96.08%, and 95.76%, respectively, with an area under the curve (AUC) of 0.987 (95% confidence interval = 0.955-0.998). Entering and exiting nerve sign was observed in 87.3% of schwannomas and in 3.0% of non-schwannoma lesions (P < 0.001), while split-fat sign was similar between the two groups (9.5% vs. 2.0%; P = 0.068).

Polar blood supply sign and target sign on elastography are specific US signs in peripheral schwannomas. The combination of two-dimensional imaging, color flow imaging, and elastography can achieve an excellent diagnostic accuracy in schwannomas.