Cancer starts when cells in the body begin to grow out of control. Cells in nearly any part of the body can become cancer, and can spread to other areas of the body. To learn more about how cancers start and spread, see What Is Cancer?
Oral cavity cancer, or just oral cancer, is cancer that starts in the mouth (also called the oral cavity). Oropharyngeal cancer starts in the oropharynx, which is the part of the throat just behind the mouth. To understand these cancers, it helps to know the parts of the mouth and throat.
The oral cavity (mouth) and oropharynx (throat)
The oral cavity includes the lips, the inside lining of the lips and cheeks (buccal mucosa), the teeth, the gums, the front two-thirds of the tongue, the floor of the mouth below the tongue, and the bony roof of the mouth (hard palate). The area behind the wisdom teeth (called the retromolar trigone) can be included as a part of the oral cavity, although it is often considered part of the oropharynx.
The oropharynx is the part of the throat just behind the mouth. It begins where the oral cavity stops. It includes the base of the 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 throughout the oral cavity and oropharynx make saliva that keeps your mouth moist and helps you digest food.
The different parts of the oral cavity and oropharynx are 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).
Cancers can also start in other parts of the throat, but these cancers aren’t discussed in this document:
- Cancers of the nasopharynx (the part of the throat behind the nose and above the oropharynx) are discussed in the American Cancer Society document Nasopharyngeal Cancer.
- Cancers that start in the larynx (voice box) or the hypopharynx (the part of the throat below the oropharynx) are discussed in the American Cancer Society document Laryngeal & Hypopharyngeal Cancer.
Tumors and growths in the oral cavity and oropharynx
Many types of tumors (abnormal growths of cells) can develop in the oral cavity and oropharynx. They fit into 3 general categories:
- Benign or non-cancerous growths that do not invade other tissues and do not spread to other parts of the body.
- Harmless growths that can later develop into cancer. These are known as pre-cancerous conditions.
- Cancerous tumors that can grow into surrounding tissues and spread to other parts of the body.
Benign (non-cancerous) tumors
Many types of benign tumors and tumor-like conditions can start in the mouth or throat:
- Eosinophilic granuloma
- Granular cell tumor
- Condyloma acuminatum
- Verruciform xanthoma
- Pyogenic granuloma
- 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. Some of them may cause problems, but they are not likely to be life-threatening. The usual treatment for these types of tumors is surgery to remove them completely since they are unlikely to recur (come back).
Leukoplakia and erythroplakia (possible pre-cancerous conditions)
Leukoplakia and erythroplakia are terms used to describe certain types of abnormal tissue that can be seen in the mouth or throat:
- Leukoplakia is a white or gray patch.
- Erythroplakia is a flat or slightly raised, red area that often bleeds easily if it is scraped.
- Erythroleukoplakia is a patch with both red and white areas.
Your dentist or dental hygienist may be the first person to spot these white or red areas. They may be a cancer, they may be a pre-cancerous condition called dysplasia, or they could be a relatively harmless condition.
Dysplasia is graded as mild, moderate, or severe, 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. For example, severe dysplasia is more likely to become a cancer, while mild dysplasia is more likely to go away completely.
The most frequent causes of leukoplakia and erythroplakia are smoking and chewing tobacco. Poorly fitting dentures that rub against the tongue or the inside of the cheeks can also cause these conditions. But sometimes, there may be no obvious cause. Dysplasia will often go away if the cause is removed.
A biopsy is the only way to know for certain if an area of leukoplakia or erythroplakia contains dysplastic (pre-cancerous) cells or cancer cells. For a biopsy, a sample of tissue from the abnormal area is removed and then looked at under the microscope. But other tests may be used first to help determine if they might be cancers (and therefore will need a biopsy) or to choose the best area to sample for a biopsy. These tests are described in the section “Can oral cavity and oropharyngeal cancers be found early?”
Most cases of leukoplakia do not develop into cancer. But some leukoplakias are either cancerous when first found or have pre-cancerous changes that can eventually progress to cancer if not properly treated.
Erythroplakia and erythroleukoplakia are less common but are usually more serious. Most of these red lesions turn out to be cancer when they are biopsied or will develop into cancer later.
However, it is important to note that most oral cancers do not develop from pre-existing lesions (either leukoplakia or erythroplakia).
Oral cavity and oropharyngeal cancers
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. These cancers begin in early forms of squamous cells, which are flat, scale-like cells that normally form the lining of the mouth and throat.
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 grown into deeper layers of the oral cavity or oropharynx.
Verrucous carcinoma is a type of squamous cell carcinoma that makes up less than 5% of all oral cancers. It is a low-grade (slow growing) cancer that rarely spreads to other parts of the body, but it can grow deeply into surrounding tissue.
If they are not treated, areas of ordinary squamous cell cancer may develop within some verrucous carcinomas. Some verrucous carcinomas may already have areas of ordinary squamous cell cancer that are not recognized in the biopsy sample. Cells from these areas of squamous cell carcinoma may then spread to other parts of the body.
For all of these reasons, verrucous carcinomas should be removed promptly, along with a wide margin of surrounding normal tissue.
Minor salivary gland carcinomas
Minor salivary gland cancers can develop in the glands in 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.
The tonsils and base of the tongue contain immune system (lymphoid) tissue, where cancers called lymphomas can start. For more information about these cancers, see the American Cancer Society documents Non-Hodgkin Lymphoma, Non-Hodgkin Lymphoma in Children, and Hodgkin disease.
The information in the rest of this document about oral cavity and oropharyngeal cancer covers only squamous cell carcinoma.
Last Revised: 01/27/2016