Oropharyngeal cancer develops in the part of the throat just behind the mouth, called the oropharynx. Sometimes this is called throat cancer. The oropharynx begins where the oral cavity stops. It includes the base of tongue (the back third of the tongue), the soft palate (the back part of the roof of the mouth), the tonsils, and the side and back wall of the throat.

The oral cavity and oropharynx help you breathe, talk, eat, chew, and swallow. Minor salivary glands located throughout the oral cavity and oropharynx make saliva that keeps your mouth moist and helps you digest food.

The oral cavity and oropharynx have several types of body tissues, and each of these tissues is made up of several types of cells. Different cancers can develop from each type of cell. The differences are important, because they can influence a person's treatment options and prognosis (outlook for survival).

There are cancers that start in other parts of the throat that aren't discussed in this document. Cancers of the nasopharynx (the part of the throat above the oropharynx) are discussed in the separate American Cancer Society document, Nasopharyngeal Cancer. Cancers that start in the hypopharynx (the part of the throat below the oropharynx) or the larynx (voice box) are discussed in the separate American Cancer Society document, Laryngeal & Hypopharyngeal Cancer.

Many types of tumors (abnormal growths of cells) can develop in the oral cavity and oropharynx. Some of them are benign, or non-cancerous, which means they do not invade other tissues and do not spread to other parts of the body. Other tumors are cancerous. They can grow into surrounding tissues and spread to other parts of the body. Some growths start off harmless but can later develop into cancer. These are known as pre-cancerous conditions.

Benign (Non-cancerous) Oral Cavity and Oropharyngeal Tumors

Many types of benign tumors and tumor-like conditions can start in the mouth or throat:

• eosinophilic granuloma 
• fibroma 
• granular cell tumor 
• keratoacanthoma 
• leiomyoma 
• osteochondroma 
• lipoma 
• schwannoma 
• neurofibroma 
• papilloma 
• condyloma acuminatum 
• verruciform xanthoma 
• pyogenic granuloma 
• rhabdomyoma 
• odontogenic tumors (tumors that start in tooth-forming tissues)

These non-cancerous tumors start from different kinds of cells and have a variety of causes, but the usual treatment is to surgically remove them since they are unlikely to recur (come back).

Leukoplakia and Erythroplakia (Possible Pre-cancerous Conditions)

Leukoplakia and erythroplakia are terms used to describe an abnormal area in the mouth or throat. Leukoplakia is a white area. Erythroplakia is a slightly raised, red area that bleeds easily if scraped. Often, your dentist or dental hygienist may be the first person to spot these problems.

These white or red areas may be a cancer, they may be a pre-cancerous condition called dysplasia, or, they could also be a relatively harmless condition. There are mild, moderate, and severe forms of dysplasia, which are distinguished from one another based on how abnormal the tissue looks under the microscope. Knowing the degree of dysplasia helps predict how likely it is to progress to cancer or to go away on its own or after treatment.

The most frequent causes of leukoplakia, and erythroplakia, are smoking or chewing tobacco. Poorly fitting dentures rubbing against the tongue or the inside of the cheeks can also cause them. Often dysplasia will go away if what is causing it is removed.

The seriousness of leukoplakia or erythroplakia can be accurately determined only by a biopsy, looking at a sample of tissue under the microscope. But other tests may be used first to help determine if they might be cancers (and therefore will need a biopsy).

• One method uses a dye called toluidine blue. The dye is spread over the abnormal area and if there is cancer, it will stain the malignant tissues blue. 
• Another method uses laser light. When the light is reflected off cancerous tissue, it looks different from the light reflected off normal tissue. 
• Another system uses a special light to view the area after the mouth has been rinsed with a solution of acetic acid (the acid in vinegar). 
• Sometimes the abnormal area can be evaluated by exfoliative cytology. In this technique, the lesion is scraped with a stiff brush (brush biopsy), and the cells from the scraping can be looked at under the microscope.

Most of the time, leukoplakia is very unlikely to develop into cancer. But about 1 out of 4 leukoplakias are either cancerous when first found or have pre-cancerous changes that eventually progress to cancer if not properly treated. Erythroplakia is usually more serious. As many as 7 out of 10 of these red lesions turn out to be cancer when they are biopsied or will develop into cancer later.

Cancerous Oral Cavity and Oropharyngeal Tumors

Several types of cancers can start in the mouth or throat.

Squamous Cell Carcinomas

More than 90% of cancers of the oral cavity and oropharynx are squamous cell carcinomas, also called squamous cell cancers. Squamous cells are flat, scale-like cells that normally form the lining of the mouth and throat. Squamous cell cancer begins as a collection of abnormal squamous cells.

The earliest form of squamous cell cancer is called carcinoma in situ, meaning that the cancer cells are present only in the outer layer of cells called the epithelium. This is different from invasive squamous cell carcinoma, where the cancer cells have spread into deeper layers of the oral cavity or oropharynx.

Verrucous Carcinoma

Verrucous carcinoma is a type of squamous cell carcinoma that makes up less than 5% of all oral cavity tumors. It is a low-grade cancer that rarely spreads to other parts of the body but can deeply spread into surrounding tissue. Therefore, it is important to surgically remove the tumor and a wide margin of surrounding tissue.

Minor Salivary Gland Carcinomas

Minor salivary gland cancers can develop in the glands that are found throughout the lining of the mouth and throat. There are several types of minor salivary gland cancers, including adenoid cystic carcinoma, mucoepidermoid carcinoma, and polymorphous low-grade adenocarcinoma. For more information about these cancers and benign salivary gland tumors, see the American Cancer Society document, Salivary Gland Cancer.

Lymphomas

The tonsils and base of the tongue contain immune system (lymphoid) tissue that can develop into a cancer called a lymphoma. For more information about these cancers refer to the American Cancer Society documents, Non-Hodgkin Lymphoma and Hodgkin Disease.

The information in the rest of this document about oral cavity and oropharyngeal cancer refers only to squamous cell carcinoma.