61 Oral Cavity Carcinoma
The lips are comprised of an external upper lip (vermilion border) and external lower lip (vermilion border) and the commissures. The oral cavity begins at the vermillion border of lips anteriorly and consists of the buccal mucosa, the upper and lower alveoli, the hard palate, the anterior two-thirds of the tongue (up to the circumvallate papillae) and the floor of the mouth to the anterior tonsillar pillars. It does not include the posterior third of the tongue, soft palate or tonsils, which are in the oropharynx.
61.1 Pathology
Although benign tumours of epithelial, salivary gland and connective tissue origin occur in the oral cavity, the majority are malignant. Over 90% of the malignant tumours are squamous cell carcinomas. Most of the remaining malignant tumours are salivary gland tumours (adenoid cystic carcinoma, mucoepidermoid tumours), or sarcomas and melanomas.
Risk factors The incidence of squamous cell carcinoma of the oral cavity varies worldwide. In the United Kingdom, it accounts for less than 2% of all malignancies, but in India it accounts for more than 40% because of the common practice of chewing betel quid or paan containing tobacco. Other aetiological factors include smoking tobacco, particularly in a pipe, and high alcohol consumption. There is also an increased incidence in patients with cirrhosis of the liver. Patients with Fanconi’s anaemia have an estimated 500-fold increased risk of developing oral cavity cancer. Carcinoma of the oral cavity may develop de novo or from a pre-malignant dysplastic lesion that appears clinically as leukoplakia, erythroplakia or a combination of the two. The presence of human papilloma virus (HPV) in oral cavity carcinoma in non-smokers tends to occur in younger patients. However, HPV-related disease does not appear as frequently in the oral cavity as it does in the oropharynx and does not proffer an improvement in prognosis.
Subsites Most patients are over the age of 40 years with a peak incidence in the sixth and seventh decades. The male to female ratio is 2:1. Malignant tumours of the oral cavity affect the anterior two-thirds of the tongue (35%), floor of mouth (35%), and less frequently the buccal mucosa, retromolar trigone, hard palate and gingivae.
Macroscopic presentation Oral cavity tumours usually present as an ulcer but may protrude as an exophytic-type lesion. Tumours of the anterior floor of mouth and alveoli tend to spread to the sub-mandibular nodes, and those from the posterior oral cavity tend to metastasise to the jugulodigastric nodes. The tongue has a well-developed lymphatic drainage. Tongue tip tumours spread to the sub-mental lymph nodes first, tumours of the lateral border of the tongue spread to the jugulodigastric nodes, but some anterior tumours may spread directly to the jugulo-omohyoid nodes. Some tumours present with no nodes palpable (N0), but the incidence of occult metastases is high, greater than 20%. In addition, second primary tumours occur in up to 30% of patients with oral cavity carcinoma. They are most commonly found in the oral cavity, but also occur in other sites in the head and neck, the oesophagus and in the lungs.
Microscopic factors Several histological subtypes exist with different prognoses such as verrucous (better prognosis) and basaloid (worse prognosis) carcinomas. Other histopathological factors that have been shown to be of prognostic importance are tumour thickness, extracapsular spread (ECS) of nodal metastasis and patterns of invasion (those cancers that have a non-cohesive invasive front and/or perineural invasion appear to be associated with an increased risk of locoregional relapse). Oral cavity tongue squamous cell carcinoma (SCC) of greater than 4-mm tumour thickness is considered to represent a greater than 20% risk of cervical lymph node metastatic involvement. ECS in cervical lymph nodes is associated with an increased risk of locoregional recurrence, distant metastasis and decreased survival.
Lip cancer Cancer of the lip is similar to that of skin cancer in its clinical behaviour. Incidence rates are around 12.7 per 100,000 in North America. It is caused by ultraviolet (UV) radiation, tobacco smoking and viruses. About 90% of tumours arise in the lower lip with 7% occurring in the upper lip and 3% at the oral commissure. SCC is the commonest histological tumour type in lip cancers, followed by basal cell carcinoma. The most common non-mucosal form of lip cancer arises from tumours of the minor salivary glands, with the upper lip being more commonly involved than the lower, in contradistinction to mucosal lip cancer.
61.2 Clinical Features
The patient may have a painful ulcer, a warty growth, halitosis and, later, trismus, difficulty in eating and speaking and referred otalgia. Alveolar tumours may interfere with denture fit. On examination, the site, size and extent of the tumour should be assessed. Tongue mobility and dental hygiene should also be noted. The neck should be examined for nodal metastases, which are present in nearly a third of patients at the time of presentation. Lip cancer usually presents with an exophytic crusted lesion and actinic damage of the surrounding lip. In all cases, the patient’s general health, comorbidity and social circumstances should be documented.
61.3 Investigations
An orthopantomogram (OPG) may demonstrate involvement of the lower alveolus by the appearance of a moth-eaten rim or an opacity of the normally lucent dental canal. It is also mandatory to have a pre-treatment dental assessment when carious teeth should be appropriately managed.
Ultrasound scan (USS) with USS-guided fine-needle aspiration biopsy is the investigation of choice in confirming the presence of nodal metastases in patients who present with an enlarged neck node.
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