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Causes Of Head And Neck Cancer
By peace | July 14, 2006
Head and neck cancers account for approximately 3 to 5 percent of all cancers in the United States. These cancers are more common in men and in people over age 50. It is estimated that about 39,000 men and women in this country will develop head and neck cancer in 2005.
Most head and neck cancers begin in the cells that line the mucosal surfaces in the head and neck area, e.g., mouth, nose, and throat. Mucosal surfaces are moist tissues lining hollow organs and cavities of the body open to the environment. Normal mucosal cells look like scales (squamous) under the microscope, so head and neck cancers are often referred to as squamous cell carcinomas. Some head and neck cancers begin in other types of cells. For example, cancers that begin in glandular cells are called adenocarcinomas.
Cancers of the head and neck are further identified by the area in which they begin:
- Oral Cavity. The oral cavity includes the lips, the front two-thirds of the tongue, the gingiva (gums), the bucca mucos (lining inside the cheeks and lips), the floor (bottom) of the mouth under the tongue, the hard palate (bony top of the mouth), and the small area behind the wisdom teeth.
- Salivary glands. The salivary glands produce saliva, the fluid that keeps mucosal surfaces in the mouth and throat moist. There are many salivary glands; the major ones are in the floor of the mouth, and near the jawbone.
- Paranasal sinuses and nasal cavity. The paranasal sinuses are small hollow spaces in the bones of the head surrounding the nose. The nasal cavity is the hollow space inside the nose.
- Pharynx. The pharynx is a hollow tube about 5 inches long that starts behind the nose and leads to the esophagus (the tube that goes to the stomach) and the trachea (the tube that goes to the lungs). The pharynx has three parts:
- Nasopharynx. The nasopharynx, the upper part of the pharynx, is behind the nose.
- Oropharynx. The oropharynx is the middle part of the pharynx. The oropharynx includes the soft palate (the back of the mouth), the base of the tongue, and the tonsils.
- Hypopharynx. The hypopharynx is the lower part of the pharynx.
- Larynx. The larynx, also called the voicebox, is a short passageway formed by cartilage just below the pharynx in the neck. The larynx contains the vocal cords. It also has a small piece of tissue, called the epiglottis, which moves to cover the larynx to prevent food from entering the air passages.
- Lymph nodes in the upper part of the neck. Sometimes, squamous cancer cells are found in the lymph nodes of the upper neck when there is no evidence of cancer in other parts of the head and neck. When this happens, the cancer is called metastatic squamous neck cancer with unknown (occult) primary.
Cancers of the brain, eye, and thyroid as well as those of the scalp, skin, muscles, and bones of the head and neck are not usually grouped with cancers of the head and neck.
Causes Of Head And Neck Cancer
Tobacco (including smokeless tobacco, sometimes called “chewing tobacco” or “snuff”) and alcohol use are the most important risk factors for head and neck cancers, particularly those of the oral cavity, oropharynx, hypopharynx, and larynx. Eighty-five percent of head and neck cancers are linked to tobacco use. People who use both tobacco and alcohol are at greater risk for developing these cancers than people who use either tobacco or alcohol alone.
Other risk factors for cancers of the head and neck include the following:
- Oral cavity. Sun exposure (lip); possibly human papillomavirus(HPV) infection.
- Salivary glands. Radiation to the head and neck. This exposure can come from diagnostic x-rays or from radiation therapy for noncancerous conditions or cancer.
- Paranasal sinuses and nasal cavity. Certain industrial exposures, such as wood or nickel dust inhalation. Tobacco and alcohol use may play less of a role in this type of cancer.
- Nasopharynx. Asian, particularly Chinese, ancestry; Epstein-Barr virus infection; occupational exposure to wood dust; and consumption of certain preservatives or salted foods.
- Oropharynx. Poor oral hygiene; HPV infection and the use of mouthwash that has a high alcohol content are possible, but not proven, risk factors.
- Hypopharynx. Plummer-Vinson (also called Paterson-Kelly) syndrome, a rare disorder that results from iron and other nutritional deficiencies. This syndrome is characterized by severe anemia and leads to difficulty swallowing due to webs of tissue that grow across the upper part of the esophagus.
- Larynx. Exposure to airborne particles of asbestos, especially in the workplace.
Immigrants from Southeast Asia who use paan (betel quid) in the mouth should be aware that this habit has been strongly associated with an increased risk for oral cancer. Also, consumption of mate, a tea-like beverage habitually consumed by South Americans, has been associated with an increased risk of cancers of the mouth, throat, esophagus, and larynx.
People who are at risk for head and neck cancers should talk with their doctor about ways they can reduce their risk. They should also discuss how often to have checkups.
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