Benign neurogenic tumors of the oral cavity

Benign neurogenic tumors of the oral cavity

Int. J. Oral Maxillofac. Surg. 1987: 1 6 : 7 0 - 7 6 (Key words: tumor, benign; tumor, neurogenic; surgery, oral and maxillofaeial) Benign neurogenic...

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Int. J. Oral Maxillofac. Surg. 1987: 1 6 : 7 0 - 7 6 (Key words: tumor, benign; tumor, neurogenic; surgery, oral and maxillofaeial)


Neurogenic tumors are rare in the oral cavity, particularly so when malignant. Traumatic neuroma, although usually included with neurogenic tumors, is a reactive process rather than a true neoplasm. Neurofibroma and schwannoma derive from nerve fibers, the perineurium, the endoneurium and the neurolemmal cells. They present histological differences. The neurofibroma may present in solitary and generalized types; the latter also known as neurofibromatosis or von Recklinghausen's disease of the skin. We here report typical cases of benign neurogenic tumors of the oral cavity. ABSTRACT

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(Accepted for publication 5 Januray 1986)

Tumors o f the peripheral nerves that appear in the oral cavity originate in the neural sheath. The majority of them are benign. Malignant neoplasms such as neurogenic sarcomas, and malignant schwannomas are rare indeed in the oral cavity. This paper reviews the recent literature regarding these tumors, and presents typical examples o f these u n c o m m o n entities that appear in the oral cavity.

Traumatic n c u r o m a Traumatic neuroma is not usually considered to be a-true tumor. It is, rather, a reactive process following the severence or simple injury o f a sensory nerve, and is characterized by hyperplasia of irregularly arranged schwann cells and neurofibrils in

a connective tissue stroma 9,~°,21,38.It was first described by ODIER in the early 19th century 31 whereas traumatic neuromas first described in the dental literature in 1930, and were related to injuries of the mental and infraorbital nerves3k Usually develop when nerve fibers are compressed against bone or are accidentally included in ligation o f vessels. They are most commonly reported after a Caldwell-Luc approach to the maxillary sinus (involving the infraorbital nerve) and extractions of teeth ~°,2~,34. Clinically, they appear as nodules that remain asymptomatic unless pressure is exerted upon them, resulting in neuralgia which decreases with local ischemia. Hypesthesia is also possible 13,14'21'34. Differential diagnosis includes schwannoma and neurofibroma. The treatment of choice is surgical excision.


Fig. 1. Bundles of peripheral nerves surrounded

by septa of dense fibrous connective tissue (H. & E. x 140).

Case report A 54-year-old man presented to the Oral and Maxillofacial Department of Apostle Paul's Accident Hospital complaining of pain of the left infraorbital region. Physical examination revealed that the area was very sensitive to palpation but was otherwise within normal limits. Past medical history was significant in that the patient was involved in a car accident 5 months previously, and had sustained a fracture of the left zygomaticomaxillary complex. It was left untreated because it did not cause any significant disfigurement and did not hinder function. Radiographic examination confirmed the fracture. The patient was admitted to the hospital with a provisional diagnosis of traumatic neuroma. 2 days following admission, the infraorbital area was explored from an intraoral approach under general anestesia. A nodule, 0.4 cm in diameter, was found in the left infraorbital foramen. It was excised and sent for histological examination (Fig. 1). The diagnosis was traumatic neuroma.

Neurofibroma A l t h o u g h some authors use the terms neuro f i b r o m a and s c h w a n n o m a to describe the same pathological entity, it is known that they represent 2 different neoplasms, which, however, derive in b o t h cases from nerve fibers, the endoneurium, the perineurium, or neurolemmal cells (schwann cells) ~,~4,2°,3s. N e u r o f i b r o m a can occur in 2 forms: the


solitary type which is m o r e common; or as a generalized neurofibromatosis, also known as von Recklinghausen's skin disease ~8,32.The solitary type m a y be peripheral or central. It usually presents in the 25-40 age group, and originates as a rule, from the sympathetic, the peripheral, or the cranial nerves. It is not c o m m o n in the oral cavity. W h e n it occurs there, it is usually located in the tongue, the lips, or the mucosa o f the h a r d palate; a l t h o u g h it m a y be found occasionally on the buccal mucosa, the edentulous alveolar crest, a n d the floor o f the mouth, as well as in the tonsillar area, the nasopharynx, the s u b m a n d i b u l a r area, and the neck 7,~2,13,19,20,32. Clinically, it usually appears as a small, sessile t u m o r with a smooth surface t h a t grows quite slowly and m a y not be diagnosed for a long time. The peripheral type is associated with neurofibromatosis in 2 0 - 6 0 % o f the cases, whereas the central type is rarely related to this disease. It is u n c o m m o n for a neurofibroma to become malignant, especially in the case o f the solitary type; although it is not as u n c o m m o n as in the case of schwannoma. Diagnosis from the clinical picture is n o t always easy; n e u r o f i b r o m a is usually asymptomatic, b u t some pain and paresthesia m a y be associated with it. There does not a p p e a r to be a sex predilection2,3,5,12,18,22,23,28,29,33. The endosteal (central) localization o f neu r o f i b r o m a is quite rare since it most commonly derives from the inferior alveolar nerve; indeed, PRESCOTT & WHITE 20 believe that the central type is found almost exclusively in the mandible, and, in a review o f the literature in 1970, they found 16 such cases and a d d e d 1 of their own 2°. In 1978, LARSON el a l ) 4 reviewed 27 cases o f central neurofibroma including 2 of their own. The radiographic picture o f endosteal neurofibr o m a varies a n d depends on the location. W h e n it involves the inferior alveolar nerve, it appears as an ovoidal osteolytic enlarge-



ment of the mandibular canal in complete continuation with the canal at both ends 12,~9. The differential diagnosis in the peripheral type includes the other neurogenic tumors; in the central type, odontogenic cysts, ameloblatomas, and other odontogenic tumors as well as malignant neoplasms, must be considered22, 29. Microscopically, neurofibroma contains elongated cells with irregular nuclei lying between bundles of collagen fibers. Unlike schwannoma, the pattern varies. Blood ves- Fig. 2. Ovoid radiolucency of the left mandibular sels, histiocytes, mast cells, fibroblasts, and canal. neurites may also be seen. The Golgi apparatus and the endoplasmic reticulum are well developed and there are numerous mito- of the left mandible. 2 days later, he was chondria and lysosomes. Neurofibroma taken to the operating room, where, under does not have a specific architectural pat- general anesthesia, a trapezoid buccal flap tern unless it resembles the Meisner tactile was raised intraorally, the mandibular bone corpuscles. It is encapsulated in only about was exposed, and the lesion was approached 4% of cases 2,7,16,26,28.The treatment of choice with fissure burs, mallet and chisels. Despite is surgical excision which, in the central some difficulties encountered from brisk type, should be followed by reapproxi- bleeding from the inferior alveolar vessels, mation of the 2 ends of the nerve, while in the lesion was removed in toto, and the the peripheral type, an adequate margin of nerve ends were reapproximated and suhealthy tissue may have to be removed in tured together. The pathologist's report some cases if the borders of the tumor are confirmed the diagnosis of neurofibroma. not well defined 12,33. Prognosis is good. The patient did well postoperatively and There is a slight possibility of malignant complained of no hypoesthesia. transformation. The tumor rarely recurs. In the solitary type, a through clinical examination and a long follow-up are required Neurofibromatosis (von so as to exclude generalized disease ~4,2°.

Recklinghausen's skin disease)

Case report A 63-year-old man was seen at the OutPatient Department of the Oral and Maxillofacial Department of Apostle Paul's Accident Hospital, referred by his dentist for a radiolucency, ovoid in shape, in continuation with the inferior alveolar nerve, a routine radiographic finding (Fig. 2). The lesion was asymptomatic. The past medical history was noncontributory. The patient was admitted to the hospital with the provisional diagnosis of central neurofibroma

This disease was first described by von Recklinghausen in 1882. It is considered to be one of the most common genetic diseases in man, affecting one in every 3,000 live births. It is transmitted as an autosomal dominant. It is characterized by multiple neurofibromas of the skine, care" au lait spots, and bony changes. In addition to the most common form, there is another form characterized by more extensive central nervous system involvement, particularly affecting the 8th cranial nerve. There can be significant bony

NEUROGENIC TUMORS changes (hyperplastic or hypoplastic) which may affect the zygoma and the temporomandibular joints resulting in gross facial asymmetry. There may also be defects of the greater and lesser wings of the spenoid, changes in the walls of the orbit, the ealvarium, and the sella turcica as a result of neurofibroms expanding along the course of the nerves. It may appear radiographically in some cases as a "cystic" lesion. The sensory function of the trigeminal nerve as well as the motor functions of the facial and hypoglossal nerves may be affected. Intraoral manifestations of the disease are not common, although, when they occur, the may displace teeth and cause macroglossia. There is a 6-29% possibility of sarcomatous transformation and an even greater risk for the development of pleochromocytoma.23,26 Case report

A 74-year-old man presented to our OutPatient Department complaining of difficulty in wearing his denture because he was biting his left cheek. Clinical examination revealed an extended, raised, mucosal surface, hard in consistency, of the left buccal area and the left aspect of the lower lip, with minor signs of trauma, apparently caused by the dentures. The patient had been suffering from neurofibromatosis (Fig. 3) with no neurological signs or radio-

Fig. 3. Multiple neurofibromas on a 74-year old

patient's body.


graphical findings, diagnosed many years previously. The raised area was considered to be a manifestation of the same disease, and this was confirmed by an incisional biopsy. The treatment plan consisted of removing the lesion and covering the area with lyophilised dura mater. 37 However, the patient had second thoughts, and would not permit the proposed operation.

Schwannoma This disease is also known as neurolemmoma, or Schwann's tumor. It is a benign tumor of neuroectodermal origin arising from the Schwann cells of the neural sheath. It affects the peripheral nervous system, the cranial nerves (except the optic and the olfactory), the spinal nerves, and the autonomic nervous system, where Schwann's cells encase the neurons and their axons. Rare as a central bone tumor, schwannoma is not uncommon as a soft tissue neoplasm in the head and neck 7,9,~3,16,34,35. The oral cavity is usually affected during the 2nd and 3rd decade, the tongue being the most common site of involvement. It appears as a slowly growing tumor that may cause pain or parestesia. It is not certain if there is a predilection for women or an equal sex distribution 6, 8. n, ~s-17.27. 36. Microscopically both the schwannoma and the neurofibroma contain elongated cells with irregular nuclei lying between bundles of collagen fibers. In the case of schwannoma, however, the pattern is not varied as in the case of neurofibroma. Indeed, 2 more or less distinct patterns can be seen, known as Antoni type A and type B. Antoni type A is characterized by Schwann cells that are closely packed, forming bundles, or arranged in rows with elongated, palisading nuclei. Free bands of amorphous substance between the rows of nuclei constitute the so-called Verocay bodies which, under the electron microscope, appear to be composed of thin



cytoplasmic processes with small amounts of collagen and basal laminar material showing frequent redoubling. Antoni type B is a mixture of Schwann cells, fibroblasts, and nerve fibers, that are widely separated, dispersed in a loose and r a n d o m fashion with a network of delicate reticulin fibers, and numerous microcystic spaces. The ground substance is myxoid. Virtually all schwannomas are encapsulated ~,4, 11,i3~I7, 22,24, 25,27,30,~4. As the schwannoma ages, degenerative changes take place, characterized by hyalinized tissue, myxoid areas, and large cystic spaces. The resulting entity is known as ancient n e u r o l e m m o m a 7,~6,3'. Malignant transformation is rare. The treatment of choice is surgical excision. Prognosis is goodlr, ~5. Case report

A 10-year-old boy presented for a swelling on the left side of his tongue (Fig. 4). It was hard in consistency and had a broad base. The preliminary diagnosis was aberrant lingual tonsillar tissue. 2 days later, it was removed under general anesthesia. The histological diagnosis was schwannoma.

Discussion Traumatic neuroma, also known as amputation neuroma, is not really a tumor, although it is usually described with neurogenic tumors, and is classified with them. It is of interest that, in the case presented, it consisted o f a late and seldom reported sequela of a fracture of the facial skeleton. In general, however, the neurogenic tumors are quite rare in and around the oral cavity and usually cause mild neurogenic symptoms, as in the case of traumatic neuroma and schwannoma, such as slight pain and paresthesia; or remain dormant, as often happens with neurofibroma. When central, as in the case of neurofibroma, it m a y cause resorption and complicate the differential diagnosis, while in multiple localizations, as in von Recklinghausen's disease, it may present with a variety of symptoms. Although schwannoma and neurofibroma are terms that have been used in the past as synonyms, they differ histologically and histogenetically, the former deriving from Schwarm cells, the latter from the fibroblasts of the perineurium. The treatment of choice in all 3 entities is surgical excision. Recurrence is usually the result of inadequate removal. Malignant transformation, which is generally rare, m a y be encountered occasionally with neurofibroma, expecially the multiple type.

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