Pathology of the Head and Neck

96 J.W. Eveson33.7.6.1 NeurofibromaICD-O:9540/0Solitary neurofibromas are relatively uncommon inthe orofacial region and tend to affect people in the20–40 years age group [189]. Most tumours are sporadic,but the possibility of neurofibromatosis type 1should always be considered when dealing with theselesions. They usually form small, painless, expansilesubmucosal nodules. The tongue is the most commonintraoral site, but occasionally they develop onthe inferior dental nerve and appear as a fusiform radiolucentarea along the course of the inferior dentalcanal.3.7.6.2 SchwannomaICD-O:9560/0Schwannoma ( neurilemmoma; neurinoma) is a benignneoplasm of Schwann cell origin. Patients are usuallyin the third or fourth decades and the tumour is morecommon in women than men. Lesions in the mouthtend to form small, painless and slow-growing swellingsand the tongue is the most common site. However,occasional cases can be several centimetres in diameter[41, 87].3.7.6.3 NeurofibromatosisICD-O:9540/0Von Recklinghausen disease or neurofibromatosis type Iis inherited as an autosomal dominant trait and the generesponsible is located on chromosome 17 [153]. It is relativelycommon and affects about 1 in 4,000 births. It isusually diagnosed before the age of 10 years because ofthe characteristic cutaneous lesions and the frequentfamily history.Clinically, it is characterised by cutaneous neurofibromasthat are usually associated with café au lait pigmentationof the skin. Lesions may be focal, but sometimesthere can be thousands of tumours and the conditionis then grossly disfiguring. The lesions are usuallypainless, but itching can be a serious problem. Therecan be overgrowth of bone and associated soft tissueleading to bizarre localised gigantism. Nearly a quarterof cases involve the head and neck, but only about 5% affectthe oral cavity.3.7.6.4 Multiple Neuromasin Endocrine NeoplasiaSyndromeICD-O:9570/0Multiple endocrine neoplasia syndrome type 2B is anautosomal dominant condition characterised by thepresence of mucosal neuromas together with medullarycarcinoma of the thyroid gland and phaeochromocytoma[147]. Nearly 90% of patients with the conditionhave point mutations at codon 918 of the RET proto-oncogene.Clinically, patients often have a Marfanoid habituswith arachnodactyly and a narrow face. Mucosal neuromasare the most consistent feature of the disease andmay be pathognomonic. They tend to form on the lateralmargins and dorsum of the tongue and appear asmultiple, small, painless nodules. These nodules may bethe first indication of the condition. The lips are sometimesenlarged and blubbery. Mucosal neuromas oftenaffect the palpebral conjunctiva and can also involve thesclera.Microscopy shows a partially encapsulated tangledmass of small nerve fibres, often with a thickened perineurium.These nerves lie in a loose fibrous stroma. Thenerves usually stain with S-100 and may stain with epithelialmembrane antigen indicating perineurial differentiation.The mucosal neuromas themselves rarely cause clinicalproblems, but may act as indicators of the more seriousaspects of the syndrome.3.7.7 Granular Cell Tumour(Granular Cell Myoblastoma)ICD-O:9580/0Granular cell tumours are uncommon, but about half ofall cases involve the head and neck region. The tongue,particularly the dorsum, is the most common site. Thepeak incidence is in middle life and 10–20% of cases aremultiple. There is a female predominance of about 2:1.They usually form nondescript, painless swellings, butoccasionally surface candidal infestation causes the lesionto present as a white plaque [59, 108]. See for thislesion also Chap. 7.3.8 Squamous Cell Carcinoma3.8.1 IntroductionSquamous cell carcinomas account for about 90% ofall malignant neoplasms in the mouth and orophar-