Cancer of the mouth and throat: Overview
The oral cavity ( mouth) and the upper part of the throat (pharynx) have roles in many important functions, including breathing, talking, chewing, and swallowing. The mouth and upper throat are sometimes referred to as the oropharynx. The important structures of the mouth and upper throat include the following:
- Inside lining of the cheeks (buccal mucosa)
- Floor of the mouth
- Back of the throat, including the tonsils (oropharynx)
- Roof of the mouth (the bony front part [hard palate] and the softer rear part [soft palate])
- Area behind the wisdom teeth
- Salivary glands
Many different cell types make up these different structures. Cancer occurs when normal cells undergo a transformation whereby they grow and multiply without normal controls.
- As the cells multiply, they form small abnormalities called lesions. Eventually, they form a mass called a tumour.
- Tumours are cancerous only if they are malignant. This means that, because of their uncontrolled growth, they encroach on and invade neighbouring tissues.
- Malignant tumours may spread to neighbouring tissues by direct invasion or by travelling along lymphatic vessels and nerves or through the blood stream.
- They may also travel to remote organs via the bloodstream.
- This process of invading and spreading to other organs is called metastasis.
- Tumours overwhelm surrounding tissues by invading their space and taking the oxygen and nutrients they need to survive and function.
Tumours in the mouth and throat include both benign and malignant types.
- Benign tumours, although they may grow and penetrate below the surface layer of tissue, do not spread by metastasis to other parts of the body.
- Benign tumours of the oropharynx are not discussed here.
Pre-malignant conditions are cell changes that are not cancer but which may become cancer if not treated.
- Dysplasia is another name for these pre-cancerous cell changes.
- Dysplasia can be detected only by taking a biopsy of the lesion - this means to collect a tiny sample of the abnormal area.
- Examining the dysplastic cells under a microscope indicates how severe the changes are and how likely the lesion is to become cancerous.
- The dysplastic changes are usually described as mild, moderately severe, or severe.
The two most common kinds of pre-malignant lesions in the oropharynx are leukoplakia and erythroplakia.
- Leukoplakia is a white or whitish area. It can often be easily scraped off without bleeding. Only about 5% of leukoplakias are cancerous at diagnosis or will become cancerous within 10 years if not treated.
- Erythroplakia is a raised, red area. If scraped, it may bleed. Erythroplakia is generally more severe than leukoplakia and has a higher chance of becoming cancerous over time.
- These are often detected by a dentist at a routine dental examination.
Several types of malignant cancers occur in the mouth and throat.
- Squamous cell carcinoma is by far the most common type, accounting for more than 90% of all cancers. These cancers start in the squamous cells, which form the surface of much of the lining of the mouth and pharynx. They can invade deeper layers below the squamous layer.
- Other less common cancers of the mouth and throat include minor salivary gland tumours and lymphoma.
- Cancers of the mouth and throat do not always metastasise, but those that do usually spread first to the lymph nodes of the neck. From there, they may spread to more distant parts of the body.
- There are more than 6,200 new cases of oral cancers diagnosed in the UK each year.
- Nearly 2,000 deaths occur each year from oral cancers in the UK
- The incidence of oral cancers has been gradually increasing in the UK over the past 25 years.
- Cancers of the mouth and throat occur in around twice as many men as women.
These cancers can develop at any age but occur most frequently in people aged 45 years and older.
Incidence rates of mouth and throat cancers vary widely from country to country. These variations are due to differences in risk factor exposures.