Head and neck cancer pathophysiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Maneesha Nandimandalam, M.B.B.S.[2]

Head and Neck cancer Microchapters
Patient Information
Overview
Classification Brain tumor Oral cancer Nasopharyngeal cancer Hypopharyngeal cancer Glomus tumor Salivary gland tumor Laryngeal cancer Thyroid cancer Parathyroid cancer Esophageal cancer
Causes
Differential diagnosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [3]

Pathophysiology

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 more susceptible to throat cancer.

Ethnicitymay also play a part, with African American men in the [U.S.]being found to be at a 50% higher risk of throat cancer than Caucasian men.

Microscopic pathology

Throat cancers are classified according to their histology or cell structure, and are commonly referred to by their location in the oral cavity and neck. This is because where the cancer appears in the throat affects the prognosis - some throat cancers are more aggressive than others depending upon their location. The stage at which the cancer is diagnosed is also a critical factor in the prognosis of throat cancer.

Squamous Cell Carcinoma

Squamous cells are the epithelium (tissue layer) that is the surface cells of much of the body. Skin and mucous membranes are squamous cells. This is the most common form of larynx cancer, accounting for over 90% of throat cancer. Squamous Cell Carcinoma is most likely to appear in males over 40 years of age with a history of heavy alcohol use coupled with smoking.

Epidimoid Cancer

(See Squamous cell carcinoma)

Adenocarcinoma

Adenocarcinoma is a cancer of the columnar epithelium typical of the lower esophagus. It is typical of Barrett's Esophagus but may be at another location. Adenocarcinoma is thought of as a product of Barrett's Esophagus.