What Are Oral Cavity and Oropharyngeal Cancers?

Cancer starts when cells in the body start to grow out of control. Cells in nearly any part of the body can become cancer, and can spread to other parts 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. This is the part of the throat just behind the mouth. Most cancers that form here are a type of cancer called squamous cell carcinoma. But other types of cancer, and other benign growths and tumors, can also form.

The oral cavity (mouth) and oropharynx (throat)

To understand these cancers, it helps to know the parts of the mouth and 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, but it's often thought of as part of the oropharynx.

The oropharynx is the part of the throat just behind the mouth. It starts 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 walls of the throat.

illustration showing location of the back wall of the oropharynx, floor of the mouth, lower lip, gums, tonsil, retromolar trigone, soft palate, hard palate

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 and throat moist and helps you digest food.

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 growths are not cancer. They do not invade other tissues and do not spread to other parts of the body.
  • Pre-cancerous conditions are harmless growths that can turn into cancer over time.
  • Cancer tumors are growths that can grow into nearby tissues and spread to other parts of the body.

Benign (not cancer) tumors

Many types of benign tumors and tumor-like changes can start in the mouth or throat, such as these:

  • 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. Some of them may cause problems, but they're 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 tissue changes 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's scraped.
  • Erythroleukoplakia is a patch with both red and white areas.

Your dentist or dental hygienist may be the first person to find these white or red patches. They may be cancer, they may be a pre-cancerous condition called dysplasia, or they could be a relatively harmless change.

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 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 common 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 changes. But sometimes, there's no clear 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. (See Tests for Oral Cavity and Oropharyngeal Cancers.) But other tests may be used first to help determine if they might be cancers (and will need a biopsy) or to choose the best area to sample for a biopsy. These tests are described in Can Oral Cavity and Oropharyngeal Cancers Be Found Early?

Most cases of leukoplakia do not turn into cancer. But some leukoplakias are either cancer when first found or have pre-cancerous changes that can 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.

Still, it's important to note that most oral cancers do not develop from pre-existing lesions (either leukoplakia or erythroplakia).

Oral cavity and oropharyngeal cancers

The different parts of the oral cavity and oropharynx are made up of many types of cells. Different cancers can start in each type of cell. These differences are important, because they can impact a person’s treatment options and prognosis (outlook).

Squamous cell carcinomas

Almost all (more than 90%) of the cancers in the oral cavity and oropharynx are squamous cell carcinomas, also called squamous cell cancers. These cancers start in early forms of squamous cells, which are flat, scale-like cells that form the lining of the mouth and throat.

The earliest form of squamous cell cancer is called carcinoma in situ. This means that the cancer cells are only in the 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's a low-grade (slow growing) cancer that rarely spreads to other parts of the body, but it can grow deeply into nearby tissue.

If not treated, areas of ordinary squamous cell cancer may develop inside some verrucous carcinomas. And some verrucous carcinomas may already have areas of ordinary squamous cell cancer in them that aren't seen 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 right away, along with a wide margin (edge) of surrounding normal tissue.

Other types of cancer in the oral cavity and oropharynx

Minor salivary gland carcinomas: these cancers can start in the glands in the lining of the mouth and throat. There are many types of minor salivary gland cancers, including adenoid cystic carcinoma, mucoepidermoid carcinoma, and polymorphous low-grade adenocarcinoma. To learn more about these cancers, as well as benign salivary gland tumors, see Salivary Gland Cancer.

Lymphomas: 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 Non-Hodgkin Lymphoma, Non-Hodgkin Lymphoma in Children, and Hodgkin Disease.

Cancers in other parts of the throat

Cancers can also start in other parts of the throat, but these cancers aren’t covered here:

  • Cancers of the nasopharynx (the part of the throat behind the nose and above the oropharynx) are covered in Nasopharyngeal Cancer.
  • Cancers that start in the larynx (voice box) or the hypopharynx (the part of the throat below the oropharynx) are covered in Laryngeal & Hypopharyngeal Cancer.

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

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Last Medical Review: March 9, 2018 Last Revised: March 9, 2018

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