Laryngeal Cancer: The Basics

What is the Larynx?

The larynx, or voice box, is an area in the throat that contains an intricate mixture of cartilage and muscles. Not only is it responsible for producing our voice, but also performs other complex functions such as protecting our airway during swallowing. The larynx is divided into three separate regions: the supraglottic larynx, the glottis, and the subglottic larynx. The glottis is the region that contains the true vocal cords, thin strips of cartilage that vibrate together to produce sound. It is protected in the front by the large thyroid cartilage, which can be felt as the "Adam's apple" in our neck. When you feel for your Adam's apple, directly under that large piece of firm cartilage is the voice box, or the glottic portion of the larynx where the true vocal cords are located. Directly above the actual voice box is the supraglottic larynx, or supraglottis. This area contains some of the lining of the throat, cartilage and muscles that control the movement of the vocal cords, and the epiglottis, which is a flap of cartilage that closes over the voice box to protect our airway during swallowing. Below the vocal cords is the subglottic larynx, or subglottis. This area is the area of the throat and airway below the vocal cords but above the trachea. All three of these areas together are considered the larynx.

What is laryngeal cancer?

The definition of a tumor is a mass of abnormally growing cells. Tumors can be either benign or malignant. Benign tumors have uncontrolled cell growth, but without any invasion into normal tissues and without any spread. A tumor is called malignant (cancer) when tumor cells gain the propensity to invade tissues and spread locally as well as to distant parts of the body. In this sense, laryngeal cancer occurs when cells in the lining of the throat grow uncontrollably and form tumors that can invade normal tissues and spread to other parts of the body.

Cancers are described by the types of cells from which they arise. Over 95% of laryngeal cancers arise from the lining of the throat (not from the actual muscle or cartilage cells) and are called squamous cell carcinomas. Approximately 5% of these are called verrucous carcinoma, which have a wart-like appearance to them and are often less aggressive and slow-growing. Although there are other cancers that can arise in the larynx (salivary gland tumors-from minor salivary glands contained in the larynx, lymphomas of the larynx, and sarcomas-from muscle and cartilage cells), the vast majority are squamous cell carcinomas. Hence, these are the most commonly studied.

In addition to invasive cancers, patients are sometimes diagnosed with precancerous lesions, called carcinoma-in-situ. These most commonly occur in the glottis itself (where the true vocals cords are), as this area is more likely to produce early signs of disease. Carcinoma-in-situ occurs when the lining of the throat undergoes changes similar to cancerous changes without any invasion into the deeper tissues. Hence, while the cells themselves have cancer-like qualities, there is no risk of spread, as no invasion has occurred.

Am I at risk for laryngeal cancer?

Laryngeal cancer occurs in approximately 12,000 Americans per year, causing about 4,200 deaths. It makes up one quarter to one third of all cancers of the throat. It has classically been thought of as a disease that affects older men. Most patients are diagnosed when they are in their fifties or sixties, and it only rarely occurs in younger people. In America, blacks have a significantly higher incidence of laryngeal cancer than do whites. In the 1950s and 1960s, 15 men had laryngeal cancer for every one woman. However, this ratio is decreasing, and in more recent studies, about five to six men are diagnosed with laryngeal cancer for every one woman. This almost certainly reflects the long-term effects of women starting to smoke as much as men.

Many risk factors have been implicated in the development of laryngeal cancer. These include chronic irritation from laryngitis or voice abuse, chronic gastric reflux, and exposure to certain chemicals, such as wood dust, nitrogen mustard, and asbestos. However, far and away the largest risk factor for the development of laryngeal cancer is smoking. Pipe smoking, cigar smoking, and cigarette smoking have all been strongly associated with the development of larynx cancer. There is also an association between heavy alcohol intake and laryngeal cancer. Although it has classically been thought of as a co-risk factor that only increases the risk of smoking, some more recent studies have shown that heavy alcohol use can increase the risk of laryngeal cancer by itself. It is estimated that heavy drinking increases the risk of laryngeal cancer by 2-6 times, while smoking increases the risk between 5-25 times, depending on how much one smokes. In a person who both smokes and drinks, the risk is increased to up to 40 times the risk of someone who neither smokes nor drinks. National public health measures have been implemented in the United States to attempt to decrease the abuse of tobacco and alcohol. Although no specific decrease has been seen yet, there is hope that these measures will lead to a decrease in the incidence of laryngeal cancers over the next 15 years.

Though there is some improvement in the smoking rates in younger people in the United States, there is still a large proportion using smokeless tobacco. This puts them at a higher risk of oral cavity, tongue, and lip cancer. People who use smokeless tobacco may also be at increased risk for developing cancer of the supraglottic larynx, although this risk is probably not as high as it is for people who smoke cigarettes, cigars, or a pipe.

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