Cancer begins in cells, the building blocks that make up tissues. Tissues make up the organs of the body.
Normal cells grow and divide to form new cells as the body needs them. When normal cells grow old or get damaged, they die, and new cells take their place.
Sometimes, this process goes wrong. New cells form when the body doesn't need them, and old or damaged cells don't die as they should. The buildup of extra cells often forms a mass of tissue called a growth or tumor.
Tumors in the mouth or throat can be benign (not cancer) or malignant (cancer). Benign tumors are not as harmful as malignant tumors:
- are rarely a threat to life
- can be removed and usually don't grow back
- don't invade the tissues around them
- don't spread to other parts of the body
- may be a threat to life
- can grow back after they are removed
- can invade and damage nearby tissues and organs
- can spread to other parts of the body
Almost all oral cancers begin in the flat cells (squamous cells) that cover the surfaces of the mouth, tongue, and lips. These cancers are called squamous cell carcinomas.
Oral cancer cells can spread by breaking away from the original tumor. They enter blood vessels or lymph vessels, which branch into all the tissues of the body. The cancer cells often appear first in nearby lymph nodes in the neck. The cancer cells may attach to other tissues and grow to form new tumors that may damage those tissues.
The spread of cancer is called metastasis. See the Staging section for information about oral cancer that has spread.
When you get a diagnosis of cancer, it's natural to wonder what may have caused the disease. Doctors can't always explain why one person gets oral cancer and another doesn't.
However, we do know that people with certain risk factors may be more likely than others to develop oral cancer. A risk factor is something that may increase the chance of getting a disease.
Studies have found the following risk factors for oral cancer:
Tobacco: Tobacco use causes most oral cancers. Smoking cigarettes, cigars, or pipes, or using smokeless tobacco (such as snuff and chewing tobacco) causes oral cancer. The use of other tobacco products (such as bidis and kreteks) may also increase the risk of oral cancer.
Heavy smokers who have smoked tobacco for a long time are most at risk for oral cancer. The risk is even higher for tobacco users who are heavy drinkers of alcohol. In fact, three out of four people with oral cancer have used tobacco, alcohol, or both.
Heavy alcohol use: People who are heavy drinkers are more likely to develop oral cancer than people who don't drink alcohol. The risk increases with the amount of alcohol that a person drinks. The risk increases even more if the person both drinks alcohol and uses tobacco.
HPV infection: Some members of the HPV family of viruses can infect the mouth and throat. These viruses are passed from person to person through sexual contact. Cancer at the base of the tongue, at the back of the throat, in the tonsils, or in the soft palate is linked with HPV infection. The NCI fact sheet Human Papillomaviruses and Cancer has more information.
Sun: Cancer of the lip can be caused by exposure to the sun. Using a lotion or lip balm that has a sunscreen can reduce the risk. Wearing a hat with a brim can also block the sun's harmful rays. The risk of cancer of the lip increases if the person also smokes.
A personal history of oral cancer: People who have had oral cancer are at increased risk of developing another oral cancer. Smoking increases this risk.
Diet: Some studies suggest that not eating enough fruits and vegetables may increase the chance of getting oral cancer.
Betel nut use: Betel nut use is most common in Asia, where millions chew the product. It's a type of palm seed wrapped with a betel leaf and sometimes mixed with spices, sweeteners, and tobacco. Chewing betel nut causes oral cancer. The risk increases even more if the person also drinks alcohol and uses tobacco.
The more risk factors that a person has, the greater the chance that oral cancer will develop. However, most people with known risk factors for oral cancer don't develop the disease.
Symptoms of oral cancer may include:
- Patches inside your mouth or on your lips:
- White patches (leukoplakia) are the most common. White patches sometimes become malignant.
- Mixed red and white patches (erythroleukoplakia) are more likely than white patches to become malignant.
- Red patches (erythroplakia) are brightly colored, smooth areas that often become malignant.
- A sore on your lip or in your mouth that doesn't heal
- Bleeding in your mouth
- Loose teeth
- Difficulty or pain when swallowing
- Difficulty wearing dentures
- A lump in your neck
- An earache that doesn't go away
- Numbness of lower lip and chin
Most often, these symptoms are not from oral cancer. Another health problem can cause them. Anyone with these symptoms should tell their doctor or dentist so that problems can be diagnosed and treated as early as possible.