Head and neck cancer

The term head and neck cancer refers to a group of biologically similar cancers originating from the upper aerodigestive tract, including the lip, oral cavity (mouth), nasal cavity, paranasal sinuses, pharynx, and larynx. Most head and neck cancers are squamous cell carcinomas, originating from the mucosal lining (epithelium) of these regions. Head and neck cancers often spread to the lymph nodes of the neck, and this is often the first (and sometimes only) manifestation of the disease at the time of diagnosis. Head and neck cancer is strongly associated with certain environmental and lifestyle risk factors, including tobacco smoking, alcohol consumption, and certain strains of the sexually transmitted human papillomavirus. Head and neck cancer is highly curable if detected early, most often through a combination of chemotherapy and radiation therapy, although surgery may also play an important role.

Classification

 Head and neck squamous cell carcinomas (HNSCC's) make up the vast majority of head and neck cancers, and arise from mucosal surfaces throughout this anatomic region. These include tumors of the nasal cavities, paranasal sinuses, oral cavity, nasopharynx, oropharynx, hypopharynx, and larynx.

 Oral cavity

 Squamous cell cancers are common in the oral cavity, including the inner lip, tongue, floor of mouth, gingivae, and hard palate. Cancers of the oral cavity are strongly associated with tobacco use, especially use of chewing tobacco or "dip", as well as heavy alcohol use. Cancers of this region, particularly the tongue, are more frequently treated with surgery than are other head and neck cancers.

  Nasopharynx

 Nasopharyngeal cancer arises in the nasopharynx, the region in which the nasal cavities and the Eustachian tubes connect with the upper part of the throat. While some nasopharyngeal cancers are biologically similar to the common HNSCC, "poorly differentiated" nasopharyngeal carcinoma is distinct in its epidemiology, biology, clinical behavior, and treatment, and is treated as a separate disease by many experts.

 Oropharynx

 Oropharyngeal cancer begins in the oropharynx, the middle part of the throat that includes the soft palate, the base of the tongue, and the tonsils. Squamous cell cancers of the tonsils are more strongly associated with human papillomavirus infection than are cancers of other regions of the head and neck.

   Hypopharynx

The hypopharynx includes the pyriform sinuses, the posterior pharyngeal wall, and the postcricoid area. Tumors of the hypopharynx frequently have an advanced stage at diagnosis, and have the most adverse prognoses of pharyngeal tumors. They tend to metastasize early due to the extensive lymphatic network around the larynx.

   Larynx

 Laryngeal cancer begins in the larynx or "voice box." Cancer may occur on the vocal cords themselves ("glottic" cancer), or on tissues above and below the true cords ("supraglottic" and "subglottic" cancers respectively). Laryngeal cancer is strongly associated with tobacco smoking.

   Trachea

Cancer of the trachea is a rare malignancy which can be biologically similar in many ways to head and neck cancer, and is sometimes classified as such.

 Most tumors of the salivary glands differ from the common carcinomas of the head and neck in etiology, histopathology, clinical presentation, and therapy, Other uncommon tumors arising in the head and neck include teratomas, adenocarcinomas, adenoid cystic carcinomas, and mucoepidermoid carcinomas. Rarer still are melanomas and lymphomas of the upper aerodigestive tract.

 Etiology

 Alcohol and tobacco use are the most common risk factors for head and neck cancer in the United States. Alcohol and tobacco are likely synergistic in causing cancer of the head and neck.  Smokeless tobacco is an etiologic agent for oral and pharyngeal cancers. Cigar smoking is an important risk factor for oral cancers as well. Other potential environmental carcinogens include marijuana and occupational exposures such as nickel refining, exposure to textile fibers, and woodworking. Cigarette smokers have a lifetime increased risk for head and neck cancers that is 5- to 25-fold increased over the general population. The ex-smoker's risk for squamous cell cancer of the head and neck begins to approach the risk in the general population twenty years after smoking cessation. The high prevalence of tobacco and alcohol use worldwide and the high association of these cancers with these substances makes them ideal targets for enhanced cancer prevention.

Dietary factors may contribute. Excessive consumption of processed meats and red meat were associated with increased rates of cancer of the head and neck in one study, while consumption of raw and cooked vegetables seemed to be protective. Vitamin E was not found to prevent the development of leukoplakia, the white plaques that are the precursor for carcinomas of the mucosal surfaces, in adult smokers.  Another study examined a combination of Vitamin E and beta carotene in smokers with early-stage cancer of the oropharynx, and found a worse prognosis in the vitamin users.

 Betel-nut chewing is associated with an increased risk of squamous cell cancer of the head and neck.

Some head and neck cancers may have a viral etiology. The DNA of human papillomavirus has been detected in the tissue of oral and tonsil cancers, and may predispose to oral cancer in the absence of tobacco and alcohol use. Epstein-Barr virus (EBV) infection is associated with nasopharyngeal cancer.  Nasopharyngeal cancer occurs endemically in some countries of the Mediterranean and Asiat, where EBV antibody titers can be measured to screen high-risk populations.  Nasopharyngeal cancer has also been associated with consumption of salted fish, which may contain high levels of nitrites.

 There are a wide variety of factors which can put someone at a heightened risk for throat cancer. Such factors include smoking or chewing tobacco or other things, such as betel, gutkha, marijuana or paan, heavy alcohol consumption, poor diet resulting in vitamin deficiencies (worse if this is caused by heavy alcohol intake), weakened immune system, asbestos exposure, prolonged exposure to wood dust or paint fumes, exposure to petroleum industry chemicals, and being over the age of 55 years. Another risk factor includes the appearance of white patches or spots in the mouth, known as leukoplakia; in about ⅓ of the cases this develops into cancer.

 The presence of acid reflux disease (GERD - gastroesphogeal reflux disease) or larynx reflux disease can also be a major factor. In the case of acid reflux disease, stomach acids flow up into the esophagus and damage its lining, making it mor