[Buttock mass and malignant sciatic nerve tumor]

Area of Science:

• Oncology
• Neurology
• Orthopedics

Background:

• Malignant peripheral nerve sheath tumors (MPNST) are rare and aggressive neoplasms.
• MPNSTs typically arise in patients with neurofibromatosis type 1 or a history of radiation therapy.

Observation:

• A 71-year-old man presented with a 6-month history of severe, burning foot pain radiating to the leg and buttock, followed by distal leg weakness.
• A large, painful buttock mass was noted, with significant motor and sensory deficits in the left leg and foot.
• Electromyography (EMG) revealed denervation and motor unit loss in the left lower extremity.
• MRI identified a 10-cm enhancing mass originating from the left sciatic nerve.

Findings:

• Subtotal surgical removal of a high-grade MPNST with a Ki67 labeling index > 60% was performed.
• Adjuvant radiation therapy was administered post-operatively.
• The tumor demonstrated aggressive local invasion into the pelvic region in the subsequent months.

Implications:

• This case underscores that sciatic nerve MPNST can manifest with rapidly progressing buttock masses and unilateral neuropathic foot pain.
• Clinicians should consider MPNST in the differential diagnosis of atypical neuropathic pain and palpable masses in the lower extremity.
• Early recognition and diagnosis are crucial for managing these rare and aggressive tumors.