MRI Findings and Diagnostic Significance of Soft Tissue Schwannomas in the Extremities

Objective: To analyze the MRI features and rare manifestations of schwannomas of the extremities to improve diagnosis. Methods: Retrospective analysis of 23 cases of schwannomas in the extremities confirmed by surgical pathology, summarizing its signs, signal characteristics and MRI enhancement. Results: Among the 23 cases, 20 were single lesions, and 3 were multiple lesions, resulting in a total of 28 lesions. The distribution of these lesions included 7 in the thigh, 9 in the calves, 4 in the armpits, 3 in the hips, and 4 each in the upper arms and forearms. Additionally, there was one lesion located in the groin. On T1-weighted imaging (T1WI), the lesions showed iso-intensity or hypo-intensity. On T2-weighted imaging (T2WI), they appeared slightly hyperintense or hyper-intense. Some lesions exhibited multiple small vesicle-like higher signals, cystic changes, and fiber spacing on T2WI. Furthermore, one lesion showed a liquid-liquid plane. The “target sign” was observed in 18 lesions (64.3%) and “neuropathic signs” were present in six lesions (21.4%). Finally, it was noted that on MRI enhancement, the lesions demonstrated uniform or uneven enhancement. The lesions were uniformly or unevenly enhanced on MRI enhancement. Conclusions: The MRI findings of schwannoma in the extremities exhibit specific characteristics. The cystic changes on T2WI also display distinct features. Recognition of rare MRI findings, such as cystic changes, liquid-liquid plane and septum, should be emphasized to enhance the accuracy of pre-diagnosing schwannomas.