Artículo Clínico

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Neurilemmomas of the oral cavity and the neck
Neurilemomas de cavidad oral y cuello

 

J.A. García de Marcos¹, J.J. Ruiz Masera², A. Dean Ferrer³, F. Alamillos Granados⁴,
F. Zafra Camacho¹, G. Barrios Sánchez¹, A. Vidal Jiménez⁵

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Abstract: Neurilemomas are benign neurogenic tumours, that derive from the neural sheath. Approximately 25 to 45 per cent of the extracraneal neurilemomas occur in the head and neck region. Neurilemomas usually occur between the third and the fourth decades of life. Neurilemoma is a sharply circumscribed, and usually small tumor. Clinically it manifests as a slow and gradually growing mass; microscopic examination is neccesary for diagnosis. Complete tumoral excision remains the treatment of choice and after this, they rarely recur. The aim of this article is to report a retrospective study, of nine cases, of oral cavity and neck neurilemomas, treated in our service of Oral and Maxillofacial Surgery, between 1997 and 2001. A series of epidemiological parameters (age, sex, location, size, symptoms, preoperative study, time between the symptom appearance and the first consultation, nerve of origin, predominant histologic pattern (Antoni A, Antoni B) and postoperative evolution) are evaluated. The review of the literature is made. Key words: Neurilemoma; Schwannoma; Oral cavity; Neck.

Resumen: Los neurilemomas son tumores neurogénicos benignos, con origen en la vaina neural. De los neurilemomas extracraneales, aproximadamente un 25 a un 45% ocurren en cabeza y cuello. La edad de afectación predominante es entre la tercera y la cuarta décadas de vida. El neurilemoma es un tumor claramente circunscrito y, generalmente, de pequeño tamaño. Clínicamente aparece como una masa de crecimiento lento y gradual. El examen microscópico es necesario para el diagnóstico. El tratamiento de elección es la escisión quirúrgica completa tumoral y después de ésta es muy rara su recurrencia. El propósito de este artículo es presentar un estudio retrospectivo, de nueve casos, de neurilemomas de cavidad oral y cuello, tratados en nuestro servicio de Cirugía Oral y Maxilofacial, entre 1997 y 2001. Hemos valorado una serie de parámetros epidemiológicos (edad, sexo, localización, tamaño, clínica, estudios previos a la cirugía, tiempo trascurrido entre aparición de síntomas y primera consulta, nervio de origen, patrón histológico predominante (Antoni A, Antoni B), y evolución postquirúrgica. Se ha realizado una revisión de la literatura. Palabras clave: Neurilemoma; Schwannoma; Cavidad oral; Cuello.

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1 Médico Residente, Cirugía Oral y Maxilofacial.
2 Médico Adjunto, Cirugía Oral y Maxilofacial.
3 Médico Adjunto, Cirugía Oral y Maxilofacial.
4 Médico Adjunto.Cirugía Oral y Maxilofacial.
5 Médico Residente. Servicio de Anatomía Patológica.
Hospital Universitario «Reina Sofía». Córdoba, España.

Correspondencia:
J.A. García de Marcos.
C/ Antonio Acuña, 10, 5ºA.
28009 Madrid, España.
E-mail: pepio2@hotmail.com

 

Introduction

Neurilemmomas are slow growing, benign neurogenic tumors that arise from the neural crest. They develop from the neural sheath of the peripheral motor, sensory and sympathetic nerves and from the cranial nerve pairs, with the exception of the optic and olfactory nerves that do not have a Schwann cell sheath.²

In 1910 Verocay first described a group of neurogenic tumors that he referred to as «neurinomas» (referred to by Colreavy³). In 1920 Antoni described two histological patterns characterized by being hypercelluar (Antoni A), and with a myxoid appearance (Antoni B) (referred to by Hegazy et al.⁴). In 1935 it was proposed that these tumors could originate from elements of the nerve sheath, and they became known as «Neurilemmomas» (referred to by Colreavy³). In addition to neurilemmomas other terms have been used to refer to them, such as schwannomas or neurinomas.⁵

The head and lateral portion of the neck are affected in most cases, and the most common source of intracranial neurilemmomas is cranial nerve VIII (acoustic neurinomas). ¹

Of the extracranial neurilemmomas, approximately 25 to 45% occur in the head and neck, but only 1% have an intraoral origin.^2,5 The most common localization is in the laterocervical region.²

It is predominant in the third and fourth decades of life, and no age group is exempt. It can affect from children to adults over the age of 80.²

The neurilemmoma is a sharply defined and generally encapsulated tumor, with an oval shape, either rounded or fusiform.^1,2

Most patients report the appearance of a slow-growing, painless mass, with no neurological symptoms, which can exist for years before the patient seeks medical attention.^2,3,6

The preoperative diagnosis of the neurilemmoma is rare,² although with digital intravenous subtraction angiography, Computed Tomography (CT) scans and Nuclear Magnetic Resonance, the probabilities are increased.¹

The diagnosis is always confirmed with a microscopic examination and the treatment of choice is surgical excision. ^1,5 Neurilemmomas very rarely experience malignant degeneration and after complete excision recurrence is very rare.^2,5

The object of the present work is to present a series of cases of neurilemmomas of the oral cavity and neck, as well as a revision of the literature.

Material and method

We present a retrospective study of nine cases, treated in our Oral and Maxillofacial Service at the University Hospital Reina Sofía, Córdoba between November 1997 and April 2001, with a diagnosis of neurilemmoma. In all cases the following were taken into account: age, sex, localization, size, clinical signs, preoperative evaluations, time between the appearance of the symptoms and the first consultation, predominant histological pattern (Antoni A, Antoni B), nerve of origin and postoperative evolution.

Results

Table 1 shows the characteristics of the cases studies. Of the nine cases five were women and four were men. The age range was between 14 and 77, and the average age was 29.33 (Table 1).

The time that had passed from the appearance of symptoms and the first consultation varied from 7 days to 10 years, with an average of 1.94 years.

The areas where there was a greater number of localizations was the neck (33.3%) and the tongue (33.3%), each with three cases, while the parapharyngeal space was affected only once (11.11%), upper lip (11.11%) and gums of the mandibular cavity (11.11%).

In all cases the clinical manifestation of the tumors was the appearance of a mass, together with dysphagia in one case and occasional pain in another (Fig. 1).

In five cases all the localizations were intraoral and no preoperative diagnostic tests were carried out (55.5%). The remainder were all cervical localizations, and FNA and CT scans were used in three cases (33.3%), and CT scan and biopsy were used in one case (11.1%) (Fig. 2).

In all cases surgical treatment was carried out, which consisted in the complete excision of the tumor, with the conservation of the nerve or nerves involved when these were affected. Case number 4 underwent a sub-maxillectomy. Case 5, with a parapharyngeal localization, underwent a previous oral transpharyngeal biopsy. For the resection of this tumor the approach was made by means of a parasynfysial osteotomy of the mandible (Fig. 3).

Determining the nerve of origin was only possible in those cases with submaxillary and jugular digastric localizations, where the tumor depended on the lingual and spinal nerves respectively. The size of the lesions varied between 2 mm, the smallest one, and 6 cm the largest one. With a average of 2.47 cm (Fig. 4).

The predominant histological pattern was Antoni A, there being a higher proportion of Antoni A to the Antoni B pattern of more than 80% in five cases (55.5%), between 60 and 80% in two cases (22.2%), and between 50 and 60% in one case (11.1%) (Fig. 5).

Only in one case (11.1%) did the Antoni B predominate the Antoni A pattern, this percentage being more than 80% (case 3) (Fig. 6).

During the postoperative period there was no recurrence or complication in any of the cases, with follow-up periods ranging from two to seven years, the average being 4.5 years.

Discussion

Neurogenic tumors represent a very low percentage within the neoplasic tumors of the head and neck.³ This heterogenic group is composed of benign tumors (neurofibromas, neurilemmomas, neuromas, neurogenic nevus and myoblastomas of granular cells) and malignant tumors (neurogenic sarcomas, malignant schwannomas, neuroepitheliomas and melanomas).^3,7

With regard to sex distribution, there are authors that do not find a significant difference between the sexes, and others that show a predilection for a certain sex.^2,8 In our series of nine cases, five were women and four were men.

Nearly all the anatomy of the head and neck has been affected by neurilemmomas, including facial soft tissues, especially in the preauricular region, forehead, orbit, scalp, lips, maxilla, mandible, floor of the mouth, tongue, paranasal sinus, nasal fossa, parotid gland, nasopharynx and larynx.²

With regard to intraoral localizations, the tongue and the floor of the mouth are areas more commonly affected.^1,5,7,9 Three of the five intraoral cases (60%) that we present had a lingual localization. The palate, buccal mucosa, lip and gums are also affected in a decreasing order.⁵ Rarely does they appear as a central lesion of the maxillas, and they appear more frequently in the mandible, the origin of this being the inferior dental nerve.^9,10,11

Daly and Roesler divided these tumors, when located in the head and neck, into two groups: medial and lateral. The lateral tumors emerge from the cervical nerve trunk and from the cervical and branchial plexus; the medial tumors emerge from the last four cranial pair of nerves and from the cervical sympathetic chain, these sometimes appearing clinically as «parapharyngeal» tumors.^1,2 In addition to this, cervical tumors have been classified according to the sternocleidomastoid muscle: from the anterior triangle and from the posterior triangle; and parapharyngeal [tumors] according to the relation with the styloid process and the muscles that originate here: from the prestyloid compartment and the poststyloid^8,12 compartment.

Locating the nerve of origin exactly can be impossible, and only about 50% of cases are correlated with their nerve of origin.^2,5 In our series we were only able to establish the nerve of origin in submaxillary localizations (lingual nerve) and jugular-digastric (spinal nerve) localizations. In the neck, when the nerve can be identified, it is the vagus as well as the cervical plexus and branchial nerves that are the most affected.²

Generally this tumor has a watery or putty-like consistency. It is small, between 0.3 and 3 cm, most being less than 5 cm, although occasionally it can grow until it reaches a diameter of 20 cm.^1,2,7 In our case series, the average size of the lesions was of 2.47 cm. The larger tumors are irregularly lobulated and they can be partially cystic, these being called cystic schwannomas or schwannomas with degenerative changes.^1,6 An increase in size can be related to an interlesional hemorrhage. ¹

It appears clinically as a painless, solitary mass, variable in size, without neurological symptoms, although on occasions it can compress the accompanying nerve as well as the neighboring structures, producing symptoms derived from the pressure such as pain and paresthesia.^1,2 In our series the most frequent clinical sign was the appearance of a mass. Dysfunction of the vocal chords, snoring, coughing, breathing difficulties, and rarely Horner’s syndrome, may appear depending on the specific anatomy of the affected region.² It can be confused with other complaints of the head and neck, such as infections or metastasic tumors.⁸ In case number 4 the diagnosis previous to surgery, was of a submaxillary tumor, as the CT scan report was of a submaxillary gland tumor and the FNA was not definitive.

In our study we carried out a CT scan only in cervical cases, as a preoperative study was not necessary in any of the intraoral cases.

In the CT scan these lesions appear hypodense compared with the muscle, and when contrast material in introduced there is a certain amount of enhancement, generally peripheral¹³ (Fig. 7).

NMR can show not only the tumor and the capsule but also, in certain cases, the nerve from which it has developed. ¹⁴ It is characterized by a signal of equal intensity to that of the muscle in T1 weighted sequences and by high signal intensity on T2.^7,13

The central neurilemmoma produces a radiolucid, welldefined, expansive and unilocular image in the orthopantomography. ^9,10

In the initial evaluation the use of FNA has been recommended. Colreavy and al. obtained a definitive preoperative diagnosis in 25% of cases.³

In our study, FNA was useful in jugular-digastric and posterior laterocervical locations (being used in 66.6% of cases).

The typical neurilemmoma has a histological pattern composed of dense, hypercellular areas and, Antoni A areas, mixed with loose hypocellular Antoni B areas.^1,2,15

In the Antoni A pattern, the cytoplasm and nuclei of the cells are fusiform and they are distributed in short fascicles. The cells can be aligned in a characteristic fashion forming nuclear palisades and Verocay bodies (two images of confronted nuclear palisades, separated by an acellular zone).^10,15

The Antoni B pattern is formed of fusiform cells similar to those of the Antoni A pattern, although fewer in number. On occasions the loose matrix, which is a characteristic of this pattern, can degenerate because of myxoid changes, into a cystic area,15 as occurred in case number 3 (Fig. 8).

In our series there was a clear predominance of the Antoni A pattern over the Antoni B, with both patterns existing in all cases.

When degenerative changes are very pronounced, calcifications, hyalinizations, hemorrhages and atypical nuclei will appear as well as cystic formations, these being called ancient neurilemmomas, but these changes do not lead to malignancy.^2,9

The electronic microscope and the immunohistochemical analysis (S-100, Leu-7) are useful for diagnosing and classifying in a precise way nerve sheath tumors.³ Neurilemmomas are stained more strongly with antibodies against the S-100 protein, which serves to differentiate them from smooth muscle tumors, which do not stain.²

Clinically and histologically the schwannoma tumor should be differentiated from the neurofribroma, which is a neurogenic tumor that arises from the cells constituting the nerve sheath. The neurofibroma is the most common tumor. It is made up of a mixture of Schwann cells and fibroblasts, and it has a greater tendency to malignancy.¹ The neurofibroma is a tumor which is generally non-encapsulated and lobulated, with an irregular surface and, unlike the neurilemmoma, which pushes away the associated nerve, it becomes intertwined with the nerve of origin^1,2,6,9,16. It is a tumor which is difficult to remove, that recurs or persists when resection has been incomplete; and in cases of hereditary neurofibromatosis, it can transform into a malignant tumor.⁹

The treatment of choice is surgical removal.¹ The neurilemmomas that appear in larger nerve trunks, should be dissected without damage to the nerve, as the nerve fibers do not form part of the tumor, that emerges from the capsule of the nerve, pushing the axons aside.^2,6 The non-encapsulated subtypes require a security margin when removed.¹ The treatment in our series, in all cases, was surgical excision of the tumor, conserving the nerve of origin in the two cases in which it could be established. In none of the cases did the process recur.

After removal of the neurilemmoma there may be a transitory or permanent neurological sequelae may appear, and information should be given as to this possibility.^6,13 Leu et al. consider the conservation and repair of the nerve a priority during tumor excision, due to the unlikely probability of malignant transformation.⁸ End-to-end anastomosis or nerve graft insertion are possible solutions, when preserving the nerve of origin is impossible.³ The use of microsurgical techniques has also been suggested for preserving the nerve and for completely removing the tumor.¹⁴

In the revision of neurilemmoma cases of the spinal cord, carried out by Seppälä et al., on 20 patients, partial excision of the tumor was performed so as to avoid harming the nerve of origin. Of these, eleven experienced recurrence with reintervention being necessary only in two of them. The study concludes that radical excision of the tumor is not justified if nerve function is compromised.¹⁷

Conclusions

Neurilemmomas are benign tumors, derived from the neural sheath, which are generally presented as slow-growing masses. Microscopic examination is required for their diagnosis and treatment entails surgical resection.

Acknowledgements

To Dr. Pérez-Seoane Orduña (Staff Departament of Pathology. University Hospital «Reina Sofía», Córdoba.

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