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NF1 – MPNST — SCE Neurology MCQ

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HardNeurogeneticsNF1 – MPNSTSCE Neurology

A 30-year-old man with NF1 develops a rapidly growing, painful mass in his left thigh along the course of the sciatic nerve. MRI shows a large, heterogeneous mass within the nerve sheath. Biopsy shows a malignant peripheral nerve sheath tumour (MPNST). What is the significance of this in NF1?

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Correct answer: B — MPNSTs are a major cause of morbidity and mortality in NF1 — they arise from pre-existing plexiform neurofibromas in approximately 8–13% of NF1 patients and are aggressive malignancies requiring wide surgical excision ± chemotherapy/radiotherapy

MPNSTs are the most feared complication of NF1, arising from malignant transformation of pre-existing plexiform neurofibromas. They are aggressive sarcomas with a 5-year survival of ~20–50%. Warning signs in NF1 patients include: rapid growth of a previously stable neurofibroma, new/increasing pain, and new neurological deficit. PET-CT can help identify suspicious lesions (MPNSTs are FDG-avid). Treatment is wide surgical excision ± adjuvant radiotherapy/chemotherapy. A: MPNSTs are malignant. C: Strongly associated with NF1. D: They can be cured if caught early. E: MPNSTs occur in NF1, not NF2.

Reference: NICE NG99; NF1 Guidelines; WHO CNS Classification