Peripheral nerve sheath tumour of the sciatic nerve
A female patient referred for MRI due to a incidentally detected soft tissue mass at duplex scan examination. She denied any discomfort and pain in the region of the lesion. Previous history was unremarkable.
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There is a fusiform T1W hypo- and T2W centrally hypo- and peripherally hyperintense lesion (target sign) in the posterior part of the thigh, closely related to the sciatic nerve. The lesion enhances vividly and homogeneously after contrast administration.
A note is made of minor medial meniscus extrusion and tibial subchondral cyst associated with cartilage degeneration. Also, a small ganglion cyst near the attachment of the lateral head of gastrocnemius muscle is evident.
According to clinical and MR findings, a diagnosis of peripheral nerve sheath tumour of the sciatic nerve was made.
An enhancing fusiform mass in continuity with a neurovascular bundle is virtually diagnostic for peripheral nerve sheath tumour. Target sign, as shown in the present case, was previously assumed to be pathognomonic of neurofibroma, however, it has been observed in both neurofibromas and schwannomas and has even been reported in malignant peripheral nerve sheath tumours.