Laryngeal neurilemmoma: a case report.

Abstract

Published reports of benign nerve sheath tumors of the larynx are extremely rare. Because these tumors represent a potential threat to the airway, prompt diagnosis and treatment are vital. We report a case of a neurilemmoma that arose from the right arytenoid muscle adjacent to the arytenoid cartilage. The mass was completely excised, and no recurrence was observed during follow-up. We discuss the diagnosis and management of this rare tumor

Introduction

Benign nerve sheath tumors of the larynx are extremely uncommon. When they do occur, they pose a potential threat to the airway, so accurate diagnosis and prompt treatment are vital. Very few reports of either laryngeal neurilemmomas (schwannomas) or neurofibromas are found in the literature. We report a case of a neurilemmoma that arose from the fight arytenoid muscle.

Case report

A 50-year-old woman was referred by her general practitioner for evaluation of a 3-month history of intermittent dysphagia. She had no history of sore throat or voice alteration, but she did experience occasional dyspepsia. She had stopped smoking 2 years earlier. She had no other significant history.

Findings on physical examination, including indirect laryngoscopy, were normal. Likewise, esophagoscopy and direct laryngoscopy revealed that the postcricoid space and esophagus were normal. However, we did make an incidental finding of a small swelling on the right arytenoid muscle adjacent to the arytenoid cartilage (figure 1). Although this finding did not explain the patient's symptoms, the lesion was excised, and histopathology revealed that it was a benign nerve sheath tumor. The excised light-yellow lesion measured 0.3 cm and was well circumscribed. Microscopic evaluation identified Antoni A areas that were made up of a proliferation of spindle-shaped stromal cells arranged in compact sheets. Characteristic Antoni B areas were also present; they featured haphazardly arranged spindle cells in looser myxoid areas (figure 2). Immunohistochemically, the spindle cells showed diffuse positivity for S-100 protein, which helped confirm the diagnosis of a laryngeal neurilemmoma.

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Postoperatively, no evidence of a laryngeal neurologic deficit was observed. The patient's voice was preserved unaltered, and her swallowing of both solids and liquids returned to normal. Although it must be assumed that we excised part of the nerve of origin along with the lesion, this resulted in no detectable neurologic dysfunction.

At the 6-month follow-up, the patient's dysphagia and dyspepsia had resolved following a short course of a proton-pump inhibitor, and repeat examinations detected no recurrence of the laryngeal swelling.

Discussion

Neurilemmomas are peripheral nerve sheath tumors derived from Schwann's cells. They are significantly more likely to affect sensory nerves than motor nerves. (1) These tumors are typically slow growing, solitary, well circumscribed, and located on the proximal nerves or spinal nerve roots. They differ from neurofibromas in that the latter are unencapsulated, they do not cause symptoms, and they may be associated with von Recklinghausen's disease. Neurilemmomas affect both sexes equally, and they occur most often during the fifth and sixth decades of life. (2) Approximately 50% of all neurilemmomas are located in the head and neck region, with the most common site being the parapharyngeal space. (3,4) Neurilemmomas of the larynx are extremely rare. One study showed that only 1 of 722 benign tumors of the larynx was a neurilemmoma. (5)

Neurilemmomas typically affect nerve sheaths but not usually nerve fibers. Symptoms, therefore, are dependent on the site of origin. Most peripheral neurilemmomas present as palpable masses; they may be painful, but they are seldom associated with a neurologic deficit. Intracranial neurilemmomas, such as acoustic neuromas, may develop within the internal auditory meatus and compress the VIIIth cranial nerve, leading to symptoms such as deafness and tinnitus.

Most neurogenic tumors of the larynx originate in either the aryepiglottic fold or the false vocal folds. (4) In these locations, the nerve of origin is likely to be the recurrent laryngeal nerve or the internal branch of the superior laryngeal nerve. As a laryngeal neurilemmoma expands, it projects into the laryngeal airway. This projection is unlikely to cause symptoms initially, but as the lesion increases in size, it may interfere with the vocal folds and give rise to dysphonia. A much larger tumor will eventually compromise the airway and lead to stridor.

No characteristic features suggest a neurilemmoma on simple inspection with the naked eye. Although computed tomography and magnetic resonance imaging have been shown to help delineate between benignity and malignancy in larger tumors, (6) the diagnosis is usually made by the pathologist. Both fine-needle aspiration and incisional biopsy have been used, but the literature indicates that excision of the tumor is the most reliable treatment. (6)

Pathologically, neurilemmomas are made up almost entirely of Schwann's cells. Three criteria are necessary to establish a histopathologic diagnosis: the presence of a capsule, the identification of Antoni A and B areas, and positivity of the tumor cells for S-100 protein. (7) The tumor in our patient met all these criteria.

Ideally, a neurilemmoma should be totally excised, but anatomic constraints sometimes make this difficult. (3,4,6) The preferred method is microlaryngeal endoscopic excision with either conventional microlaryngoscopy instruments or a C[O.sub.2] laser. An open approach may be necessary for larger lesions. In fact, surgeons should individualize the treatment of each laryngeal tumor, keeping in mind the need for maintaining mucosal integrity. Some authors feel that preoperative tracheotomy is mandatory for patients with larger tumors. (6) The preferred surgical approaches for removal of laryngeal neurilemmomas are the transhyoid approach, the laryngofissure approach, and the lateral pharyngotomy approach. The lesion in our patient was completely excised via a standard microlaryngoscopic technique. The airway was secured with an endotracheal tube that had a small diameter and therefore did not impede the excision. Minimal bleeding occurred during the procedure.

Although it is rare, neurilemmoma must be included in the differential diagnosis of laryngeal swellings.

References

(1.) Gentry LR, Mehta RC, Appen RE, Weinstein JM. MR imaging of primary trochlear nerve neoplasms. AJNR Am J Neuroradiol 1991;12:707-13.

(2.) Morris JU. Peripheral nerve tumors. In: Cotran RS, ed. Robbins Pathologic Basis of Disease. 6th ed. Philadelphia: W.B. Saunders; 1999:1445-6.

(3.) Takumida M, Taira T, Suzuki M, et al. Neurilemmoma of the larynx: A case report. J Laryngol Otol 1986;100:847-50.

(4.) Sanghvi V, Lala M, Borges A, et al. Lateral thyrotomy for neurilemmoma of the larynx. J Laryngol Otol 1999;113:346-8.

(5.) New GB, Erich JB. Benign tumors of the larynx. A study of 722 cases. Arch Otolaryngol 1938;28:841-910.

(6.) Meric F, Arslan A, Cureoglu S, Nazaroglu H. Schwannoma of the larynx: Case report. Eur Arch Otorhinolaryngol 2000;257:555-7.

(7.) Enzinger FM, Weiss SW. Benign tumors of the peripheral nerves. In: Enzinger FM, Weiss SW. Soft Tissue Tumors. St. Louis: Mosby; 1988:725-35.

Jonathan R. Newton, MRCS; Robert W. Ruckley, FRCS; Ursula M. Earl, FRCP 

From the Department of Otolaryngology (Dr. Newton and Dr. Ruckley) and the Department of Pathology (Dr. Earl), Darlington Memorial Hospital, Sheffield, U.K.

Reprint requests: Dr. Jonathan R. Newton, 17 Queens Mansions, Queens Ave., Aberdeen AB15 6WA, UK. Phone: [phone]; fax: [phone]; e-mail: [e-mail]