Neoplastic Conditions

Benign tumours: squamous cell papilloma commonly occurs on the lips, cheeks and tongue and is often associated with viral warts on the hands. Neurilemmoma, neurofibroma and the granular cell tumour are not infrequently encountered. Lipoma presents as a mucosal polyp, clinically similar to a fibroepithelial polyp. Benign tumours of salivary gland origin arise in the upper lip and in the palate, usually at the junction between the hard and soft palates, the commonest of which is the pleomorphic adenoma. Benign salivary tumours are rare in the tongue and floor of mouth; most salivary tumours in the lower parts of the oral cavity are adenocarcinomas.

Malignant tumours: as at other sites in the upper aerodigestive tract, tobacco and alcohol use are the major risk factors for oral cancers. Their effects are related to dose and duration of use; together they have a multiplicative rather than additive effect. Recent interest has focussed on the role of viruses in oral malignancy. Certain forms of Human Papillomavirus have been detected in a proportion of tumours but their precise role in oncogenesis is unclear.

Squamous epithelial dysplasia: a rare finding; most lesions of the oral mucosa are not dysplastic. As with invasive tumours, epithelial dysplasia is strongly associated with tobacco smoking and alcohol use but paradoxically lesions arising in patients who do not use tobacco are most likely to develop carcinoma. In contrast to the cervix with which it has often - probably erroneously - been compared, oral dysplastic lesions are frequently hyperkeratotic with varying degrees of epithelial hyperplasia and/or atrophy. The grade of dysplasia can vary from mild to severe. Development of invasive squamous cell carcinoma seems to occur more frequently with increasing degrees of cytological disturbance (less than 5% for non-dysplastic lesions and low-grade dysplasia; around 50% for high-grade dysplasia) but there are no agreed criteria for grading or recognisable features of prognosis. Identifying high-grade dysplasia highlights the considerable risk of synchronous or metachronous squamous cell carcinoma but other factors such as site and the clinical appearance of the lesions need to be considered. Conservative surgery or ablative therapy (e.g., by laser or photodynamic therapy) will often be attempted but the effects of treatment are difficult to evaluate.

Intraoral squamous cell carcinoma: accounts for over 85% of primary malignant tumours in the mouth. Males are affected at least twice as often than females and most patients are aged between 40 and 60 years. Smoking and alcohol use are the main risk factors. The commonest intraoral sites are the lateral border/ventral surface of the anterior two-thirds of tongue (35%) and the floor of mouth (20%), followed by the mandibular gingiva/retromolar trigone, soft palate, buccal mucosa/buccal commissure and hard palate/maxillary gingiva. Tumours of the tongue and floor of the mouth tend to metastasise frequently to neck nodes - up to 30% of patients with carcinoma of the tongue and floor of mouth who have clinically negative necks will have metastatic disease. Tumours of the hard palate rarely involve nodes.

Histological and reportedly prognostic variants of squamous cell carcinoma include verrucous carcinoma, papillary squamous cell carcinoma (better than usual type), spindle cell squamous cell carcinoma, adenoid squamous cell carcinoma (same prognosis), basaloid squamous cell carcinoma and adenosquamous cell carcinoma (worse prognosis).

Prognosis: outcome for patients with intraoral squamous cell carcinoma depends on the precise anatomical site within the mouth (the further back in the mouth, the worse the outcome), the size of the tumour and the presence of regional nodal metastasis. Lymph node metastasis is the most significant factor in determining prognosis; extracapsular spread from affected nodes is also an indicator of limited prognosis, with increased risk of recurrence in the neck and of distant spread. The size and anatomical site of the tumour affects the ability to achieve surgical clearance with the risk of local recurrence but the pattern of tumour invasion is probably the most significant factor in determining lymph node metastasis. As with all upper aerodigestive tract malignancies, co-morbidity from cardiovascular and respiratory disease due to the effects of age, tobacco and alcohol use is a major adverse factor in survival.

Five-year survival with node-negative tongue carcinomas is approximately 50% falling to around 20% for patients with large tumours and positive nodes.

Squamous cell carcinoma of the lip: arising on the vermilion border of the lower lip although a few are seen on the upper lip. Probably represents a cutaneous rather than intraoral malignancy, as it is associated with long solar exposure. Less than 20% involve lymph nodes. Easily amenable to early detection and surgical excision, the five-year survival is in excess of 80%.

Squamous cell carcinoma involving either upper or lower lip but arising within the oral cavity (e.g., from the buccal commissure) is a true intraoral cancer, strongly associated with tobacco use. There is a greater likelihood of nodal metastasis but the prognosis is still reasonably good in comparison with similar lesions at other intraoral sites.

Other malignant tumours in the oral cavity include malignant lymphoma (usually a deposit of disseminated nodal disease), salivary gland types of adenocarcinoma, malignant melanoma (palate and maxillary gingiva), rhabdomyosarcoma (around the soft palate), and Kaposi's sarcoma (junction of hard and soft palate). The oral mucosa may be involved by direct spread from a malignant tumour in the minor salivary glands or from the nasal cavity/maxillary sinus.

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