neurilemoma

Neurilemoma, also known as neurinoma or schwannoma, is a benign neoplasm arising from Schwann cells of the nerve sheath. It can develop along any peripheral nerve and, less commonly, in the central nervous system. Most lesions are solitary; multiple lesions may occur with neurofibromatosis type 2 or other nerve sheath tumor syndromes.

Macroscopically the tumor is usually well circumscribed and encapsulated, compressing the involved nerve rather than invading it. Histologically it shows two Schwannian patterns known as Antoni A (cellular, palisading, with Verocay bodies) and Antoni B (loose, myxoid). The neoplastic cells are typically S-100 protein positive.

Clinically, presentation depends on the site and the extent of nerve involvement. Peripheral lesions may present as a slow-growing, painless mass with possible neuropathic symptoms in the affected distribution. Cranial nerve schwannomas, especially vestibular schwannomas, cause hearing loss, tinnitus, dizziness, or facial numbness; spinal schwannomas can cause radicular pain or weakness.

Diagnosis relies on imaging and histology. Magnetic resonance imaging (MRI) is the modality of choice, showing a well-defined, enhancing mass along a nerve. Computed tomography can aid in certain skull-base and spinal locations. Definitive diagnosis is by histopathology, often obtained after biopsy or surgical excision.

Management ranges from observation for small, asymptomatic tumors to surgical excision with nerve-sparing techniques. Radiotherapy or radiosurgery is used for unresectable tumors or residual disease, particularly in vestibular schwannomas. Prognosis after complete excision is generally favorable; recurrence is uncommon, though NF2-associated and multifocal disease carries ongoing risk.