Cancer of the larynx (Laryngeal cancer, Squamous Cell Carcinoma of the Larynx)

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What is Cancer of the larynx?

Larynx cancer (squamous cell carcinoma of the larynx). In oncology squamous cell cancers of the head and neck are often considered together because they share many similarities - in incidence, cancer type, predisposing factors, pathological features, treatment and prognosis. Up to 30% of patients with one primary head and neck tumour will have a second primary malignancy.

The larynx or "voice box" is the organ containing the vocal cords. It is made up of a complex arrangement of muscles, cartilages and ligaments, all lined by epithelium: stratified squamous epithelium on the vocal cords; and ciliated columnar epithelium on the remainder. The larynx is found in the front part of the neck, level with the C3 to C6 vertebrae (in the spinal column). It is actually a part of the air passages, and communicates with both the mouth and nose through the pharynx. It is continuous with the trachea (the main wind-pipe leading to the lungs) and acts as a conduit enabling air to enter and leave the lungs. It also acts as a valve to prevent food (and other foreign material) from entering the lungs. The larynx produces sounds through movements of the muscles and cartilages controlling the vocal cords. This changes the pitch of the vibrating column of air. The words that we speak are generated through the modification of these sounds by the lips, tongue and mouth.

Who gets Cancer of the larynx?

Larynx cancer is uncommon, but it accounts for more than 20% of all cases of head and neck cancer and occurs with increasing age. The highest incidence of larynx cancer is in the 7th decade. Larynx cancer tends to occur at a younger age in women. It can occasionally be found in children with sex incidence being strongly male predominant - particularly in areas where the incidence of larynx cancer is highest.

Geographically, the larynx tumour is found worldwide, but there is significant variation in incidence. Areas of highest incidence include Brazil, Hong Kong, Poland and Italy. In all areas the incidence is higher in urban districts than in rural areas.

Predisposing Factors

All cancers of the head and neck show a strong association with alcohol consumption and tobacco smoking, particularly of cigarettes - in fact, tobacco is thought to be implicated in well over 80% of cases of larynx cancer. Chronic exposure of the epithelial surfaces of the head and neck to these irritants are thought to result in a "field cancerisation" sequence of hyperplasia, dysplasia and carcinoma. That is, the development of premalignant lesions that may then undergo malignant change to become a cancer. Smoking and alcohol act synergistically in the development of larynx cancer - the risk when both of these factors is present is more than double the risk of exposure to one factor alone.

There is a dose-response relationship between exposure to tobacco smoke and the development of larynx cancer - the more you smoke the greater the risk. Smokers are up to 25 times more likely to larynx cancer than their non-smoking counterparts. Passive smoking, tobacco chewing and cigar smoking are also risk factors for the development of larynx cancer. Up to the point of development of overt carcinoma, many of the changes associated with cigarette smoking will reverse if the patient quits smoking.

Alcohol consumption as a risk factor for the development of larynx cancer also shows a dose-response relationship - with heavy drinkers being at greater risk. In addition, drinkers of spirits may be at a greater risk than those who drink wine.

Chronic viral infection is also associated with the development larynx cancer carcinoma. The Epstein-Barr Virus is strongly associated with the development of nasopharyngeal cancer, whilst Human Papilloma Virus, Herpes Simplex Virus and Human Immunodeficieny Virus have been associated with the development of a number of different cancers of the larynx. This is thought to be due to their interference with the function of tumour suppressor genes and oncogenes.

Other risk factors of larynx cancer include immune deficient states (such as post solid-organ transplant); occupational exposures to agents such as asbestos and perchloroethylene; radiation; dietary factors; a genetic predisposition to the development of the disease; and poor oral hygiene.

Progression

This type of larynx tumour spreads by local extension, through the destruction of adjacent tissue, and by lymphatic invasion with spread to the cervical lymph nodes. Later haematogenous spread to the lungs, liver, adrenals and kidney may occur but these are rare at the time of diagnosis.

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