Cancer develops when there is a growth of abnormal, malignant cells in part of the body. When these abnormal cells grow out of control in the head and neck region, it is diagnosed as head and neck cancer.

The areas of the head and neck have some of the largest surfaces where the inside of the body is exposed to the outside environment, providing access for breathing and eating. As a result, these areas have mucosal surfaces that line body cavities and are designed to move substances smoothly while protecting body tissues from foreign substances. In the head and neck area, these cavities include the mouth, nose, throat and sinuses. Most head and neck cancers begin in the squamous cells that line these mucosal surfaces. 

Normal mucosal cells look like flat, platelike scales (squamous) under the microscope. Because head and neck cancer usually starts in these cells, it is often called squamous cell carcinoma. A small percentage of head and neck cancers develop in other types of cells. For example, adenocarcinomas start in glandular cells, such as those in the salivary glands, rather than squamous cells.

In addition to the type of cell affected by the cancer, head and neck cancer is identified by the location in which it originates. Head and neck cancers can be located in the following areas:

• Oral cavity
• Salivary glands
• Nasal and sinus cavities
• Pharynx
• Larynx
• Lymph nodes in the upper part of the neck (if the cancer has spread)

Some cancers are not grouped with head and neck cancers even though they are in this area of the body. They include:

• Brain cancer
• Eye cancer
• Thyroid cancer
• Esophageal cancer
• Cancers of the scalp, skin, muscles and bones of the head and neck

According the National Cancer Institute (NCI), head and neck cancers account for approximately 3 to 5 percent of all the cancers in the United States. The American Cancer Society (ACS) estimated that more than 45,000 Americans will develop some form of head and neck cancer in 2007. Of that number, more than 34,000 cases will be oral or oropharyngeal cancer, while about 11,000 will be laryngeal cancer. The ACS estimates that more than 7,500 deaths from oral and pharyngeal cancer will occur in 2007.

The prognosis of head and neck cancers varies because they vary greatly in their stages. Staging determines whether a cancer is contained in the place where it first developed or has spread (and, if so, how far it has spread). It also indicates the size of the tumor and other information vital to diagnosis, treatment and prognosis. Head and neck cancers have a number of different ways they are staged based on the type of cancer cells involved, the area affected by cancer and other factors. Local cancers are confined to the area of origin. Regional cancer has extended to surrounding organs and tissues and may involve regional Lymph nodes. Metastatic cancer has spread to distant parts of the body. 

For oral and oropharyngeal cancers, the five-year survival rate for all stages is 60 percent. For laryngeal cancers, the five-year survival rates range from 36 to 83 percent, depending on the stage.