Objectives: Schwannomas (neurilemmoma) are benign solitary tumors which arise from the Schwann cells of the neural sheath. They often originate from the VIII cranial nerve. Extracranially, 25% of all schwannomas are located in the head and neck. Intraoral development is uncommon and a location in the tongue has so far only in some individual cases described.
Methodology: We present a case of a young patient, with a schwannoma, on the right side, close to the tip of the tongue.
Results: The tumor had grown slowly producing no symptoms. The diagnosis was made by histological examination. The treatment was exclusively surgical and enucleation of the mass was uncomplicated, without further recurrence.
Conclusions: We would like to add a further case of a Schwannoma of the tongue, thus allowing the possibility of being considered in the general diagnosis.
Schwannomma, neurilemmoma, tongue, our experience
Schwannomas, also referred to as neurilemmomas or neurinomas are benign, solitary encapsulated nerve sheath tumors. The tumor arises from the perineural Schwann cells and is usually attached to, or surrounded by a nerve (1, 2, 3, 4, 5, 6). As nerves exit the brain and spinal cord, there is a change between myelination by oligodendrocytes to myelination by Schwann cells. These form a thin barrier around each extracranial nerve fiber and wrap it with an insulating membrane – myelin sheath – to enhance nerve conduction. Schwannomas arise when Schwann cells are proliferated and form a tumor mass encompassing motor and sensory peripheral nerves – unknown etiology (2).
Schwannomas occur both intracranially and extracranially. Intracranially the acoustic nerve is the most common site and VIII cranial nerve schwannomas constitute the majority of them in humans (1, 3, 5, 6). Extracranial sites of these tumors are fairly rare. Extracranially, about 25% of all schwannomas, are located in the head and neck. The lateral cervical region is the most common site but only 1% shows an intraoral origin (1, 2, 3, 7). Nearly 150 cases of schwannoma of the oral cavity have been reported in the literature according to the most recent and important case collection (8) but such tumors of the tongue area are an extremely rare occurrence and were scarcely described (1, 3, 4, 5, 6, 8, 9).
The rarity of the lesion in the tongue area is the main reason why we would like to add a further case of a Schwannoma of the tongue and describe its histopathological features, thus allowing the possibility of being considered in the general diagnosis.
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An 18-year-old young man presented to the Department of Otolaryngology at the Demokrition University of Thrace for evaluation of a painless swelling on the right side, close to the tip of the tongue, first noted 2 years earlier. The swelling had slowly but progressively grown. There were no particular disturbances in swallowing, speech, taste, or sensory abnormalities. The patient complained only of the encumbrance of such a mass. His past medical history was unremarkable (Figure 1).
Clinical examination revealed an oval, freely movable, nonulcerated, 3.5 X 2 cm mass, on the right side, close to the tip of the tongue, which also was rubbery and non-tender on palpation (Figure 1). The remainder of the ENT examination was unremarkable. No lymph nodes were found in the neck.
An excisional biopsy was decided and done under local anesthesia. The operative procedure was in fact easy to do, because the mass reached from incising the right ventral part of the tongue, was easily separated from the surrounding muscles (enucleation) and did not appear to be connected with any particular structure (Figure 3). The postoperative course was uneventful. In the year following the surgery there has not been evidence of recurrence and the patient is free of symptoms.
The specimen was measured 3.1 X 1.8 X 1.5 cm and had a tan – grey multilobulated surface and homogenous on the cut section (Figure 4). Histologic sections stained with hematoxylin-eosin revealed the nature of the lesion which had the characteristic features of a benign tumor arising from the cells sheathing axonal nerves: Schwann cells. The lesion was predominantly formed of hypercellular areas of densely packed spindle cells with a typical palisading arrangement of their nuclei (Antoni A areas) with little stoma matrix. These palisades were in many points juxtaposed to form the known Verocay bodies (Figure 5).
A smaller component of the lesion was hypocellular (Antoni B areas) with no definite architecture in a loose cellular network with myxoid stroma (Figure 5). The tumor was enclosed in a thin connective tissue capsule and did not show areas of necrosis, atypia or mitosis.
Schwannomas, being rare in the oral cavity, represent a lesion not often encountered in clinical practice. Although rare, the dorsum of the tongue is the most common location in the mouth, with the tip, as in our case, being the least affected part. The palate, buccal mucosa, lip, and gingival are also affected (2, 4, 5, 10, 11).
The identification of an originating nerve may be difficult. In more than 50% of intraoral lesions it is not possible to differentiate between tumors of the lingual, hypoglossal, and glossopharyngeal nerves (1, 3, 5). In our case no associated nerve was identified. A schwannoma can occur at any age with the highest incidence between the third and sixth decades. The sex incidence is equal (1, 2, 3, 5, 6, 12).
The presenting feature of a tongue schwannoma is usually a painless tumor mass. They grow slowly pushing aside surrounding tissues. Disturbances to swallowing, taste, speech, or respiration are rare and depend on the location or the size of the tumor (1, 2, 5, 11).
Clinically schwannoma is indistinguishable from other encapsulated benign tumors in the same site. It is usually a single, circumscribed lesion mass of variable size with a hard – elastic consistency. Usually the size ranges from 0.5 to 3.0 cm. Ulceration of the overlying mucosa is rare and generally the result of trauma (1, 3, 5).
The diagnosis is confirmed by microscopic examination. Two histomorphologic patterns of schwannoma are known to coexist: Antoni A and Antoni B. In the Antoni A pattern closely packed cells with spindle-shaped nuclei are arranged in parallel rows, producing the typical palisading effect, with little stroma matrix. Between the rows there are fine cytoplasmic fibrils with acellular eosinophilic masses known as Verocay bodies. In the Antoni B pattern the tumor is less densely cellular with myxoid or edematous stroma. The cells are of various sizes but lacking an organized architecture. This pattern is usually unilocular but may be multilobular. The distinction between benign and malignant schwannomas is based on the morphological features common to all tumors of soft tissues: cellular atypia, necrosis, mitoses (1, 2, 3, 4, 5).
The diagnosis can some times be made preoperatively from a cytological examination of fine – needle aspirated biopsy material. CT or MRI is not necessary in cases where an excisional biopsy is easy to access. They are helpful for the estimation of the tumor margins in cases where the tumor is extremely bulky or located in the base of the tongue (1, 3).
The differential diagnosis includes malignant lesions such as squamous cell carcinomas and sarcomas and such benign lesions as lipomas, traumatic fibromas, leiomyomas, neuromas, adenomas, lymphangiomas, hemangiomas, granular cell tumors, salivary gland tumors, inflammatory lesions and lingual thyroid (2 ,3, 5, 7). The differentiation of schwannoma from neurofibroma is essential because an apparently “solitary” neurofibroma may be a manifestation of neurofibromatosis (4). The former derives from Schwann cells, the later from the fibroblasts of the perineurium. Virtually all schwannomas are encapsulated in contrast to neurofibroma which is encapsulated in only about 4% of cases (11).
Treatment is always surgical and complete excision results in no recurrence (2, 4, 11). Route of access is through the mouth (usually enucleation, as in our case), with the minimum of discomfort for the patient and without leaving scarring sequelae (1, 5, 6, 13). If transoral excision is not possible – for bulkiest lesions or those located at the base of the tongue – several surgical approaches are available (5).
Malignant schwannomas and malignant transformation of benign schwannomas are extremely rare and from a practical point can be discounted. On the other hand, in up to 16% of patients with neurofibromatosis, malignant changes will occur in one or more lesions (2, 3, 4, 5, 6, 7, 13, 14).
Presenting the above case, we would like to add another case of a Schwannoma of the tongue, in order to offer the possibility of being considered, diagnosed, and treated in the general practice.
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