Int. J. Oral Maxillofac. Surg. 1987: 1 6 : 7 0 - 7 6

(Key words: tumor, benign; tumor, neurogenic; surgery, oral and maxillofaeial)

Benign neurogenic tumors of the oral cavity

NICHOLAS ZACHARIADES, MICHAEL MEZITIS, ELEFTHERIOS VAIRAKTARIS, DEMETRIUS TRIANTAFYLLOU, CORNELIA SKOURA-KAFOUSSIA, ELINA KONSOLAKI-AGOURIDAKI, EFTYCHIA HADJIOLOU AND DEMETRIUS PAPAVASSILIOU.

Oral and Maxillofacial Department, Apostle Paul's Accident Hospital, Kifissia, Athens, Greece

ABSTRACT - - 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 peri- neurium, the endoneurium and the neurolemmal cells. They present histo- logical differences. The neurofibroma may present in solitary and general- ized types; the latter also known as neurofibromatosis or von Reck- linghausen's disease of the skin. We here report typical cases of benign neurogenic tumors of the oral cavity.

(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 uncommon entities that appear in the oral cavity.

Traumatic ncuroma

Traumatic neuroma is not usually con- sidered 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 cen- tury 31 whereas traumatic neuromas first de- scribed 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 maxil- lary 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 de- creases with local ischemia. Hypesthesia is also possible 13,14'21'34. Differential diagnosis includes schwannoma and neurofibroma. The treatment of choice is surgical excision.

NEUROGENIC TUMORS 71

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 Acci- dent Hospital complaining of pain of the left infraorbital region. Physical examination re- vealed that the area was very sensitive to pal- pation 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 un- treated because it did not cause any significant disfigurement and did not hinder function. Radiographic examination confirmed the frac- ture. The patient was admitted to the hospital with a provisional diagnosis of traumatic neur- oma. 2 days following admission, the infraorbital area was explored from an intraoral approach under general anestesia. A nodule, 0.4 cm in di- ameter, was found in the left infraorbital for- amen. It was excised and sent for histological examination (Fig. 1). The diagnosis was trau- matic neuroma.

Neurofibroma Although some authors use the terms neur- o f ibroma and schwannoma to describe the same pathological entity, it is known that they represent 2 different neoplasms, which, however, derive in bo th cases from nerve fibers, the endoneur ium, the perineurium, or neurolemmal cells (schwann cells) ~,~4,2°,3s. Neurof ib roma can occur in 2 forms: the

soli tary type which is more common; or as a generalized neurof ibromatosis , also known as von Reckl inghausen 's skin dis- ease ~8,32. The soli tary type may be peripheral or central. I t usually presents in the 25-40 age group, and originates as a rule, f rom the sympathetic, the per ipheral , or the cranial nerves. I t is not c o m m o n in the oral cavity. When it occurs there, it is usually located in the tongue, the lips, or the mucosa of the hard palate; a l though it may be found occasionally on the buccal mucosa, the ed- entulous alveolar crest, and the floor of the mouth, as well as in the tonsi l lar area, the nasopharynx, the submandibu la r area, and the neck 7,~2,13,19,20,32. Clinically, it usually ap-

pears as a small, sessile tumor with a smooth surface tha t grows quite slowly and may not be d iagnosed for a long time. The peripheral type is associated with neurofib- romatosis in 20-60% of the cases, whereas the central type is rarely related to this dis- ease. I t is uncommon for a neurof ibroma to become malignant , especially in the case of the soli tary type; a l though it is not as uncommon as in the case of schwannoma. Diagnosis from the clinical picture is not always easy; neurof ibroma is usually asymptomatic , bu t some pain and par- esthesia may be associated with it. There does not appear to be a sex predilec- tion2,3,5,12,18,22,23,28,29,33.

The endosteal (central) localization o f ne- u rof ib roma is quite rare since it most com- monly derives f rom the inferior alveolar nerve; indeed, PRESCOTT & WHITE 20 believe that the central type is found almost exclus- ively in the mandible , and, in a review of the l i terature in 1970, they found 16 such cases and added 1 of their own 2°. In 1978, LARSON el a l ) 4 reviewed 27 cases of central neurof ibroma including 2 of their own. The radiographic picture of endosteal neurofib- roma varies and depends on the location. When it involves the inferior alveolar nerve, it appears as an ovoidal osteolytic enlarge-

72 ZACHARIADES ET AL

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, ame- loblatomas, 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- sels, histiocytes, mast cells, fibroblasts, and neurites may also be seen. The Golgi appar- atus and the endoplasmic reticulum are well developed and there are numerous mito- chondria and lysosomes. Neurofibroma does not have a specific architectural pat- tern unless it resembles the Meisner tactile corpuscles. It is encapsulated in only about 4% of cases 2,7,16,26,28. The treatment of choice is surgical excision which, in the central type, should be followed by reapproxi- mation of the 2 ends of the nerve, while in the peripheral type, an adequate margin of healthy tissue may have to be removed in some cases if the borders of the tumor are not well defined 12,33. Prognosis is good. There is a slight possibility of malignant transformation. The tumor rarely recurs. In the solitary type, a through clinical exam- ination and a long follow-up are required so as to exclude generalized disease ~4,2°.

Case report A 63-year-old man was seen at the Out- Patient Department of the Oral and Maxil- lofacial Department of Apostle Paul's Acci- dent Hospital, referred by his dentist for a radiolucency, ovoid in shape, in continu- ation with the inferior alveolar nerve, a rou- tine radiographic finding (Fig. 2). The lesion was asymptomatic. The past medical his- tory was noncontributory. The patient was admitted to the hospital with the pro- visional diagnosis of central neurofibroma

Fig. 2. Ovoid radiolucency of the left mandibular canal.

of the left mandible. 2 days later, he was taken to the operating room, where, under general anesthesia, a trapezoid buccal flap was raised intraorally, the mandibular bone was exposed, and the lesion was approached with fissure burs, mallet and chisels. Despite some difficulties encountered from brisk bleeding from the inferior alveolar vessels, the lesion was removed in toto, and the nerve ends were reapproximated and su- tured together. The pathologist's report confirmed the diagnosis of neurofibroma. The patient did well postoperatively and complained of no hypoesthesia.

Neurofibromatosis (von Recklinghausen's skin disease) This disease was first described by von Re- cklinghausen 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 neurofibro- mas 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 73

changes (hyperplastic or hypoplastic) which may affect the zygoma and the temporo- mandibular 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 ealvari- um, and the sella turcica as a result of neur- ofibroms 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 hypo- glossal nerves may be affected. Intraoral manifestations of the disease are not com- mon, 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 Out- Patient Department complaining of difficul- ty in wearing his denture because he was biting his left cheek. Clinical examination revealed an extended, raised, mucosal sur- face, 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 bi- opsy. The treatment plan consisted of re- moving 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 neurolemmo- ma, or Schwann's tumor. It is a benign tu- mor 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 ol- factory), the spinal nerves, and the auto- nomic 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 cav- ity is usually affected during the 2nd and 3rd decade, the tongue being the most com- mon 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 neurofibro- ma contain elongated cells with irregular nuclei lying between bundles of collagen fi- bers. In the case of schwannoma, however, the pattern is not varied as in the case of neurofibroma. Indeed, 2 more or less dis- tinct patterns can be seen, known as Antoni type A and type B. Antoni type A is charac- terized 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 Ver- ocay bodies which, under the electron microscope, appear to be composed of thin

74 ZACHARIADES ET AL

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 random 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~I 7, 22, 24,

25, 27, 30, ~4. As the schwannoma ages, degener- ative changes take place, characterized by hyalinized tissue, myxoid areas, and large cystic spaces. The resulting entity is known as ancient neuro lemmoma 7,~6,3'. Malignant t ransformat ion 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 lin- gual tonsillar tissue. 2 days later, it was removed under general anesthesia. The his- tological diagnosis was schwannoma.

Fig. 4. Schwannoma of the left side of the tongue in a 10-year old boy.

Discussion Traumatic neuroma, also known as ampu- tation neuroma, is not really a tumor, al- though it is usually described with neuro- genic tumors, and is classified with them. It is o f 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 symp- toms, as in the case of t raumatic 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 may 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. Al- though schwannoma and neurof ibroma are terms that have been used in the past as synonyms, they differ histologically and his- togenetically, the former deriving f rom Sch- warm cells, the latter f rom 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 t ransformation, which is gener- ally rare, may be encountered occasionally with neurof ibroma, expecially the multiple type.

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