Cancerous Growths
Each year, cancerous growths of the mouth (oral cancer) develop in 30,000 people in the United States and cause 8,000 deaths, mostly in people older than 40. Oral cancer represents more than 2% of all cancers and 1.5% of all cancer-related deaths--a high rate considering the size of the mouth in relation to the rest of the body.
Because early detection vastly improves the likelihood of cure, screening for oral cancer should be an integral part of medical and dental examinations. Cancerous growths less than ½ inch across usually can be cured. Unfortunately, most cancerous growths are not diagnosed until they are larger and have spread to the lymph nodes under the jaw and in the neck. Because of delayed detection, 25% of oral cancers are fatal.
Risk Factors
A hereditary factor, although not yet well understood, makes certain people more susceptible to developing oral cancer. The two greatest controllable risk factors for developing oral cancer are tobacco and alcohol use. Tobacco use--including smoking cigarettes (particularly more than 2 packs per day), cigars, or pipes; chewing tobacco; and dipping snuff--accounts for 80 to 90% of all oral cancers. Cigars and cigarettes are equally dangerous as risk factors in the development of oral cancer, followed in descending order by chewing tobacco and pipe smoking.
Chronic or heavy alcohol use (particularly more than 6 drinks per day) increases the risk of oral cancer. The combination of tobacco and alcohol is more likely to cause cancer than either one alone. There is some evidence that the alcohol contained in mouthwash can contribute to oral cancer. Therefore, people who smoke and drink alcohol should choose a mouthwash that contains the lowest concentration of alcohol (which is stated on the label).
People who have had oral cancer are at risk of recurrence. Hereditary predisposition may contribute to recurrence, as may the radiation used to treat the cancer. People who continue to use tobacco and alcohol after developing oral cancer have more than twice the chance as the rest of the population (30% vs. 12%) of developing a second oral cancer.
Other factors that add to the risk of oral cancer include repeated irritation from the sharp edges of broken teeth, fillings, or dental prostheses (dentures). Syphilis, if untreated for many years, may give rise to tongue cancer, the only cancer that forms on the top of the tongue. Sun damage can cause cancer of the lip (see Section 18, Chapter 214).
About two thirds of oral cancers occur in men, but increased tobacco use among women over the past few decades is gradually closing the gender gap. As with most cancers, risk increases with age.
Types of Oral Cancer
Squamous cell carcinoma is the most common type of oral cancer. Nearly 40% of squamous cell carcinomas affect the lower lip; many of the remainder affect the floor of the mouth or the tongue. These cancers form a hard lump or a firm-bordered sore (ulcer) that may bleed intermittently. Affected areas may appear white, red, or mixed white and red and can be smooth or raised. Another type of cancer is called verrucous (warty) carcinoma, which appears as a white grooved surface on the mucosa (lining of the mouth).
Other types of cancer are less common, such as malignant melanoma and Kaposi's sarcoma. Malignant melanoma is usually associated with a history of sunburns and occurs on the surface of the skin. However, it occasionally occurs in the mouth, most commonly on the roof of the mouth, usually as a result of spread from a skin site. A malignant melanoma often has uneven, irregularly shaped borders and ranges in color from dark blue or brown to black. Its color may be spotty, however, or even speckled. As with most cancers, it occasionally bleeds. Kaposi's sarcoma is a cancer of the blood vessels near the skin and in the lining of the mouth and throat (see Section 18, Chapter 216). In people with AIDS, when Kaposi's sarcoma occurs in the mouth, it usually occurs on the roof of the mouth. The tumor is usually purple or brown and is slightly raised.
Cancers of the salivary glands are much less common than noncancerous growths. The most common cancer is mucoepidermoid carcinoma, which typically forms in a minor (small) salivary gland on the roof of the mouth. It may also occur as a lump in one of the major (large) salivary glands, either under or behind the lower jaw.
Cancers of the jawbone include osteosarcoma and metastatic tumors (those that have spread to the jaw from another part of the body).
Symptoms
Oral cancers are usually painless for a considerable length of time but eventually do cause pain. Pain usually starts when the cancer erodes into nearby nerves. When pain from cancer of the tongue or roof of the mouth begins, it usually occurs with swallowing, as with a sore throat.
The early growth of salivary gland tumors may or may not be painful. When these tumors do become painful, the pain may be worsened by food, which stimulates the secretion of saliva. Cancer of the jawbone often causes pain and a numb or pins-and-needles sensation (paresthesia), somewhat like the feeling of a dental anesthetic wearing off. Cancer of the lip or cheek may first become painful when the enlarged tissue is inadvertently bitten.
Squamous cell carcinomas often look like open sores (ulcers) and tend to grow into the underlying tissues. Cancers of the lip and other parts of the mouth often feel rock hard and are attached to the underlying tissues, whereas most noncancerous lumps in these areas are freely movable. A person who chews tobacco or uses snuff may develop white, ridged bumps on the insides of the cheeks that can develop into verrucous (warty) carcinoma. Cancerous tumors tend to grow fast and feel hard. Cancer beginning in the small salivary glands commonly appears as a small swelling.
Discolored areas on the gums, tongue, or lining of the mouth may be signs of cancer (see Section 8, Chapter 113). An area in the mouth that has recently become brown or darkly discolored may be a melanoma. Sometimes a brown, flat, freckle-like area (smoker's patch) develops at the site where a cigarette or pipe is habitually held in the lips.
Diagnosis
Oral cancers are suspected because of their appearance and symptoms. Doctors must distinguish a melanoma from normal pigmentation or from discoloration due to other causes. However, only a biopsy (removal of a tissue specimen for examination under a microscope) can determine whether a suspicious area is cancerous.
X-rays cannot always distinguish jaw cancers from cysts, noncancerous bone growths, or cancers that have spread from elsewhere in the body. However, x-rays may show irregular borders of jaw cancer and can show the loss of parts of neighboring teeth, which is characteristic of a rapidly growing cancer.
Prevention
Avoiding excessive alcohol and tobacco use can greatly reduce the risk of most oral cancers. Smoothing rough edges from broken teeth or fillings is another preventive measure. Some evidence indicates that antioxidant vitamins, such as vitamins C and E, may provide added protection, but further study is needed. Staying out of the sun reduces the risk of lip cancer. If sun damage covers a large area of the lip, a lip shave in which all of the outer surface is removed, either by surgery or with a laser, may prevent a progression to cancer.
Prognosis and Treatment
Cancers originating in or around the mouth can spread to nearby lymph nodes, which become hard and swollen. Spread of cancers to more distant parts of the body is uncommon with squamous cell carcinoma but is more likely with osteosarcoma and is very likely with malignant melanoma, which can reach organs such as the brain.
The cure rate for squamous cell carcinoma is high if the entire cancer and the surrounding normal tissue is removed before the cancer has spread to the lymph nodes. On average, 68% of people survive at least 5 years after the diagnosis. However, if the cancer has spread to lymph nodes, the 5-year survival is only 25%. Regrettably, cure rates for squamous cell carcinoma have not improved much over the past several decades. However, verrucous carcinoma is rarely fatal because it develops late in life and grows slowly. The 5-year survival rate for malignant melanoma is only 5 to 10%.
For squamous cell carcinoma and most other types of oral cancer, the mainstays of treatment are surgery and radiation therapy. These two treatments are often used together, particularly for larger cancers. For malignant melanoma, surgery is the main approach because the cancer is generally not responsive to radiation therapy.
During surgery, the extent of the cancer can be determined. The lymph nodes under and behind the jaw and along the neck may be removed. Consequently, surgery for oral cancers can be disfiguring and psychologically traumatic. Newer methods are being used, however, to minimize disfigurement. In the case of the lips, the Mohs' technique--a method of determining the extent of disease during different phases of surgery by examining each slice of tissue under the microscope after its removal--minimizes disfigurement, as does the use of lasers to destroy cancer cells. Reconstructive surgery can improve function and restore normal appearance after the disease is controlled. Missing teeth and jaw parts can be replaced with prosthetic parts.
A person with oral cancer may receive radiation therapy after surgery or just radiation therapy. Although radiation may not always be curative, especially if the cancer is extensive, it is sometimes used to shrink the cancer and thus relieve symptoms (palliation). Radiation therapy often destroys the salivary glands and leaves the person's mouth dry, which can lead to cavities and other dental problems. If the salivary glands have not been destroyed, saliva production usually recovers several weeks after the radiation treatment is completed. Because jawbones exposed to radiation do not heal well, dental problems should be completely treated before radiation is administered. Any teeth likely to become problematic are removed, and time is allowed for healing before radiation.
Good dental hygiene is critical for people who have had radiation therapy for oral cancer; the mouth heals poorly if dental surgery, such as tooth extractions, is ever needed. Such hygiene includes regular examinations and thorough home care, including daily home fluoride applications. If the person eventually has a tooth pulled, hyperbaric oxygen therapy may help the jaw heal without the death of bone and surrounding soft tissue in the area that receives the radiation (osteoradionecrosis).
Chemotherapy has been shown to have little value in the treatment of most oral cancers. For malignant melanoma, chemotherapy is used if surgery is not possible, but it generally only delays death and is usually not curative.
| 
