Schwannoma presenting in the soft palate of a nine-year-old boy

Case history

A healthy 9-year-old boy was urgently referred to the Paediatric Dental Department at the Charles Clifford Dental Hospital in Sheffield by his General Dental Practitioner with a 3-week history of a non-painful swelling of the soft palate. There was no history of trauma (physical or chemical) and, only recently, the patient reported that the lesion had gradually increased in size and was interfering with eating and swallowing. Past medical history and systemic enquiry reported nothing of note and extra-oral examination was unremarkable. Intra-oral examination revealed a non-carious mixed dentition. Furthermore, a solitary firm swelling was noted, measuring approximately 1 cm in diameter just to the right of the midline at the junction of the hard and soft palate (Figure 1). Closer examination revealed this was well demarcated by an erythematous zone. The overlying mucosa demonstrated slight ulceration with evidence of sloughing.

Subsequently, the patient was urgently referred to the Oral and Maxillofacial Department for further assessment and treatment. As part of the consultation, screening haematological and biochemical investigations were undertaken which were all found to be within the normal reference range.

At the time of presentation a flexible nasoendoscopy was preformed under local anaesthetic to determine if there was any involvement of the naso-pharynx (Figure 2).

Owing to the lesion's presentation and following examination, it was decided to arrange for an urgent excisional biopsy to be performed under general anaesthesia and a diagnosis made histopathologically. Under anaesthesia, an excisional biopsy was performed, with care taken to obtain a clear margin but not to perforate the soft palate. No attempt was made to suture the area, instead haemostasis was achieved using electro-cautery and the area allowed to granulate during healing. The specimen was then sent for histological examination. The report subsequently detailed the appearance of alternating patterns of Antoni A and Antoni B tissues with a rich infiltrate of acute and chronic inflammatory cells. This diagnosis was consistent with a benign schwannoma (Figure 3). Following surgery the patient made an uneventful recovery and was discharged. Subsequently, the patient was placed under regular review to assess healing and determine if any recurrence had occurred. To date there has been no evidence of any recurrence.

Discussion

Schwannomas, also known as neurilemmoma or neurolemmoma were clinically first described by Verocay in 1908.1 Later, in 1935, Stout recognized the histological origins of the tumour from Schwann cells, giving it the term schwannoma.2 Embryologically, Schwann cells arise during the fourth week of development from cells of the neural crest. Many nerve fibres are enveloped by Schwann cells, forming the myelin sheath that provides insulation and aids nerve conduction.

Schwannomas are described as benign, well encapsulated, slow growing lesions commonly occurring on the trunk, upper extremities and the head and neck region. Commonly, they occur as solitary lesions, however, multiple lesions have been reported in association with neurofibromatosis in von Recklinghausen disease. These are characterized by multiple skin neurofibromas and pigmentation. Head and neck schwannomas account for approximately 25% of all schwannomas,3 and of these only 1% are found intra-orally. Generally, it is thought that the tongue has the most common involvement4 (Table 1).

Schwannomas characteristically grow painlessly unless they attain a sizeable dimension and impinge on surrounding tissues, causing pressure symptoms. Depending on the site and adjacent anatomy, schwanommas have been known to cause facial paralysis and Horner's syndrome. Intra-oral symptoms can also include paraestheisa, obstructive symptoms including dysphagia, or can have an impact during mastication.

Schwanommas have not been associated with any known aetiological factor and may develop at any age, although they have been reported to occur more often during the second and third decades of life with no particular gender predilection.5

If completely excised, schwanommas show no recurrence, with malignant transformation almost never occurring.6 Those reported were either mainly in association with radiation therapy or von Recklinghausen disease.7 However, as with any undiagnosed mass, malignancy should always form part of the differential diagnoses until excluded (Table 2).

Despite these solitary tumours rarely recurring, long-term follow-up is required so as to exclude generalized disease and, as a result, the slow growing nature of the lesion. In this particular case, the patient made an uneventful recovery and has shown no sign of recurrence at 1-year follow-up. (Figure 4).