Neurilemmoma (Schwannoma)

Updated: Oct 03, 2024
  • Author: Ian D Dickey, MD, FRCSC, LMCC; Chief Editor: Harris Gellman, MD  more...
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Overview

Practice Essentials

Neurilemmomas (neurilemomas) are benign, encapsulated tumors of the nerve sheath. Their cells of origin are thought to be Schwann cells derived from the neural crest (see the image below) [1] ; accordingly, they are often referred to as schwannomas. These masses usually arise from the side of a nerve, are well encapsulated, and have a unique histologic pattern.

The cell of origin for a neurilemmoma is the SchwaThe cell of origin for a neurilemmoma is the Schwann cell, which is derived from the neural crest. These cells line the peripheral nerve processes.

This benign lesion essentially manifests itself with cosmetic deformity, a palpable mass, symptoms similar to a compressive neuropathy, or some combination of these. Neurologic symptoms tend to present late. Symptoms can be vague, and there is an average interval of up to 5 years before the diagnosis is established.

Rare descriptions exist of malignant change in long-standing neurilemmomas. Malignant change is extremely rare in isolated lesions.

Like most benign tumors, neurilemmomas respond well to local resection. Interlesional resection is warranted when complete resection would result in permanent neurologic deficit. Local control is usually excellent. Effective use of stereotactic radiosurgery (SRS) for these types of lesions has been reported. [2, 3, 4] Endoscopic approaches have been used for schwannomas of the head and neck. [5, 6]

In unusual cases where resection would lead to a significant functional deficit, these benign lesions can be merely observed.

Etiology

The cause of these neoplasms is unknown. [7] Neurilemmoma can be associated with von Recklinghausen disease; when this is the case, multiple tumors often are present.

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Epidemiology

Neurilemmoma is the most common neurogenic tumor, but precise prevalence figures have not been establsihed. These tumors affect persons aged 20-50 years. No racial or sex predilection is recognized. Common locations for neurilemmomas are, in order of decreasing frequency, the head and neck, [8] the flexor surfaces of the upper and lower extremities, and the trunk. [9]

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Prognosis

Recurrence is unlikely after complete resection. Patients usually have rapid and complete relief of pain, with excellent long-term results. [10]

Rare descriptions exist of malignant change in long-standing neurilemmomas, usually in patients with an underlying diagnosis of neurofibromatosis. Malignant change is extremely rare in isolated lesions.

Kano et al evaluated tumor control and hearing preservation relating to tumor volume, imaging characteristics, and nerve and cochlear radiation dose after SRS with a Gamma Knife (Elekta, Stockholm, Sweden) in patients with acoustic neuroma. [11]  At a median of 20 months, no patients required further treatment. Serviceable hearing was preserved in 71% of all patients and 89% of those with Gardner-Robertson (GR) class I hearing. Patients whose cochlear radiation dose was lower than 4.2 Gy had significantly better-preserved hearing of the same GR class, and all 12 patients younger than 60 years whose cochlear radiation dose was lower than 4.2 Gy had serviceable hearing at 2 years.

A systematic review and meta-analysis (nine studies; N = 1275) by Brito et al assessed hearing preservation and quality of life (QoL) in patients with small to medium-sized vestibular schwannomas treated either with a conservative wait-and-scan (WAS) approach (n = 674) or with SRS (n = 601). [12]  For the primary outcomes, serviceable hearing and pure-tone average, WAS was found to yield better results. The same was true for the secondary outcome, the Penn Acoustic Neuroma Quality of Life Scale (PANQOL) total score. The investigators noted the need for higher-quality studies.

A study (N = 243) by Pruijn et al evaluated health-related QoL (HRQoL) in patients with stable or growing vestibular schwannomas that were treated with either WAS (n = 73) or SRS (n = 170). [13]  The investigators found no statistically significant or clinically relevant differences in HRQoL between the two treatment approaches in these patients.

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