Benign peripheral nerve sheath tumor of digit versus major-nerve: Comparison of MRI findings

To compare the symptoms and magnetic resonance imaging (MRI) findings between digital peripheral nerve sheath tumor (PNST) and major-nerve PNST.

A total 36 cases with benign PNSTs (16 digital, 20 major-nerve) were enrolled. Chief complaint and Tinel sign were reviewed. Five classic MRI features of PNST, the signal intensity (SI), the enhancement, and the shape of tumor were evaluated on MRI.

Half of each group showed tenderness. Tinel sign was less frequent in digital PNST (12.5%) than major-nerve PNST (95.0%, P < 0.001). Split fat sign, entering and exiting nerve, target sign, and thin hyperintense rim were only observed in major-nerve PNST (P = <0.001, <0.001, 0.492, and 0.002, respectively). Fascicular sign was found in digital PNSTs (31.3%), but more frequent in major-nerve PNST (P < 0.001). In digital PNSTs, mild hyperintense SIs (56.2%) on T1-weighted images (T1-WI) was noted, but none in major-nerve PNST (P < 0.001). Both groups showed hyperintense SIs on T2-WI (P = 0.371). Homogeneity on T2-WI was noted in 43.8% of digital PNSTs, but none in major-nerve PNSTs (P = 0.004). Both groups showed heterogeneous enhancement (P = 0.066), but four (25%) digital PNSTs showed homogeneous enhancement. Lobulated shape was noted in 50% of digital PNSTs but none of major-nerve PNSTs (P = 0.001). Digital nerve was involved at 81.3% of digital PNSTs. Three foot cases showed unusual manifestations: bone destruction, skin thickening, and subungual location.

In digital PNSTs, Tinel sign is not commonly found and classic MRI findings is insufficient. In addition, some digital PNSTs show different SI and enhancement from major-nerve PNSTs. However, digital soft tissue tumor involving digital neurovascular bundle and especially representing a fascicular sign should be considered the possibility of a digital PNST.