Description

A 40-year-old woman was referred with an 8-month history of fullness of the right posterior thigh. This was associated with pain, primarily on sitting and occasional radicular pain down the ipsilateral leg. On examination a mobile, firm lump was identified that was tender to palpate and which also elicited a shooting pain down the leg on examination. MRI demonstrated a well-defined multiloculated mass 9 cms×6 cms which appeared to arise from the sciatic nerve, raising suspicion for a schwannoma (figure 1). A biopsy confirmed the diagnosis of schwannoma. Surgical excision was undertaken, carefully dissecting the lesion from the sciatic nerve (figure 2). The patient had an uneventful postoperative recovery without neurovascular deficits.

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Figure 1

A coronal (A) and axial (B) T1-weighted MRI of a well-defined multiloculated mass 9 cms×6 cms arising from the sciatic nerve.

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Figure 2

Schwannoma lesion excised en masse.

A schwannoma is the most common benign peripheral nerve sheath tumour composed of Schwann cells.1 It represents 8% of all soft tissue tumours with sciatic nerve involvement being <1%.2 Symptoms of nerve sheath tumours relate to nerve function and surrounding structures. Direct compression from large lesions can present with symptoms similar to those of sciatica. The diagnoses of sciatic nerve-associated schwannomas are typically made with MRI often subsequent to a normal lumbar spine MRI. Treatment of this epineurium encapsulated tumour is by delicate excision, en masse and nerve preservation followed by histopathology for definitive diagnosis.