Schwannomas are rare, slow growing, usually solitary benign nerve sheath tumours originating from ectodermal Schwann cells.1
25% to 48% occur in the head and neck region.2
Malignant transformation has been noted when schwannoma is associated with neurofibromatosis type I,3
but is exceedingly rare with sporadic schwannoma.4
Head and neck schwannomas usually involve the vestibulocochlear nerve with bilateral involvement diagnostic for neurofibromatosis type II. Only 1% occur in the oral cavity5
and only five cases involving the palatine tonsil are reported in the global literature.1 6–9
Symptoms arise due to a mass effect exerted by the tumour on surrounding structures.
MRI scanning is the modality of choice in evaluating neural tumours,5
however CT scanning provides adequate presentation of the anatomy. The radiological features with either modality are not diagnostic.
Tissue biopsy is the investigation of choice for achieving a diagnosis in nerve sheath tumours as shown in this case.
Macroscopically schwannomas are usually encapsulated lesions. Histologically they are characterised by a biphasic pattern with mixed hypercellular (Antoni A) and hypocellular (Antoni B) areas, both usually being present. In the hypercellular areas palisaded nuclei are frequently seen, so-called Verocay bodies.
The treatment of choice for benign schwannoma is surgical enucleation without the need for excision of surrounding structures.2
Where possible all such tumours should be excised to avoid the risk of malignant transformation.