Peripheral Nerve Tumors
Peripheral nerve tumors are a group of benign or malignant masses arising from the sheath cells of peripheral nerves (Schwann cells, perineural fibroblasts). The most common benign tumors are schwannoma and neurofibroma; malignant peripheral nerve sheath tumor (MPNST) is a rare but aggressive cancer. Treatment is essentially surgical; the prognosis is excellent for benign tumors but poor for MPNST.
最終更新: 2026-06-07
Definition
Peripheral nerve tumors are neoplasms arising from the sheath cells of the nerve (particularly Schwann cells and perineural fibroblasts). The great majority are benign; schwannoma (neurilemmoma) and neurofibroma are the most common. Malignant peripheral nerve sheath tumor (MPNST) is rare but is a high-grade, aggressive sarcoma. The clinical picture consists of a slowly growing mass, numbness/weakness in the nerve distribution, distally radiating paraesthesia on tapping the mass (Tinel's sign) and variable pain.
Schwannoma
Schwannoma is the most common benign peripheral nerve tumor. It arises from Schwann cells, is encapsulated and pushes the nerve fibres outward without infiltrating them (eccentric); it can therefore usually be separated from the nerve and removed completely. It is generally solitary and slow-growing; some patients have pain and a Tinel sign, while neurological deficit is uncommon. On MRI it appears as a well-defined, encapsulated mass along the course of the nerve; the 'split-fat' and 'target' signs are typical. Treatment is microsurgical excision; complete removal with preservation of the nerve fibres is achievable in a high proportion of cases, and recurrence is very rare.
Neurofibroma
Neurofibroma is a benign tumor composed of Schwann cells, perineural cells and fibroblasts. Unlike schwannoma it is unencapsulated and infiltrates between the nerve fibres; complete removal is therefore difficult and the risk of nerve damage is higher. It is strongly associated with neurofibromatosis type 1 (NF1, von Recklinghausen disease). The plexiform neurofibroma, which involves nerve plexuses, is specific to NF1 and carries a risk of malignant transformation. Treatment in symptomatic cases is surgical (partial or complete excision); in NF1-related, inoperable plexiform neurofibroma, the MEK inhibitor selumetinib is a treatment option.
Malignant Peripheral Nerve Sheath Tumor (MPNST)
MPNST is a rare but aggressive high-grade sarcoma arising from Schwann cells. A significant proportion of cases occur on a background of NF1, often as malignant transformation of an existing plexiform neurofibroma. A rapidly growing mass, severe and persistent pain and progressive neurological deficit are typical. In NF1 patients, rapid growth, new or increasing pain and hardening of an existing neurofibroma are warning signs of malignancy. MRI shows a heterogeneous, infiltrative and large mass; PET-CT shows high metabolic activity and is used in staging. Definitive diagnosis is established by biopsy and histopathological examination.
Diagnosis
Diagnosis is made by clinical examination, imaging and, where necessary, histopathological examination. The history covers the duration of the mass, its growth rate, the characteristics of any pain and a history of NF1 (cafe-au-lait spots, multiple neurofibromas, family history). MRI is the gold-standard imaging modality; it helps define the location and size of the tumor, its relationship to the nerve and the distinction between benign and malignant. Ultrasound is helpful for superficial tumors, and PET-CT for suspected malignancy and staging. EMG/nerve conduction studies are performed when there is a neurological deficit and for surgical planning. In suspected malignancy, tissue is sampled by core-needle or open biopsy; immunohistochemistry (S-100 and other markers) supports the diagnosis.
Treatment
For benign tumors, treatment is surgical. In schwannoma the tumor is removed from within its capsule by microsurgical dissection, with the nerve fibres largely preserved. Because neurofibroma is infiltrative, partial excision (debulking) or complete excision together with nerve grafting/repair as needed is performed. In small, asymptomatic tumors, observation (watch and wait) may be preferred. In selected cases such as acoustic (vestibular) schwannoma, stereotactic radiosurgery is an alternative. For MPNST, treatment is multidisciplinary: the mainstay is wide excision with negative surgical margins; adjuvant radiotherapy reduces the risk of local recurrence in high-grade, large or margin-positive tumors; chemotherapy is used in selected and metastatic cases.
Prognosis
For benign tumors the prognosis is excellent; recurrence after complete removal of a schwannoma is very rare, whereas recurrence is somewhat more frequent in neurofibroma, and follow-up is required for malignant transformation, particularly in the plexiform type. For MPNST the prognosis is poor; the risk of local recurrence and distant metastasis (most often to the lung) is high, and regular follow-up is required. Lifelong surveillance of NF1 patients is important for early detection of MPNST and for treatment success. The treatment plan is individualised for each patient, and no outcome can be guaranteed in advance.
参考文献
- Greenberg MS. Greenberg's Handbook of Neurosurgery. 10th ed. Thieme; 2023:768-776.
- Winn HR, ed. Youmans Neurological Surgery. 6th ed. Saunders; 2011:2519-2540.
- Kim DH, Murovic JA, Tiel RL, Moes G, Kline DG. A series of 397 peripheral neural sheath tumors: 30-year experience at Louisiana State University Health Sciences Center. J Neurosurg. 2005;102(2):246-255.
- Ferner RE, Gutmann DH. International consensus statement on malignant peripheral nerve sheath tumors in neurofibromatosis. Cancer Res. 2002;62(5):1573-1577.
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