Oral cavity cancer is a member of the family of head and neck cancers, also known as upper aerodigestive tract cancers. It is characterized by the appearance, development and spread of abnormal cells in the oral cavity. It mainly affects the following regions and structures:

• The inside of the mouth, including the tongue, the mucous membrane that lines the inside of the cheeks, the buccal floor (under the tongue), the buccal ceiling (hard palate) and the soft palate;
• The gums;
• The upper and lower lips;
• The salivary glands;
• The tonsils;
• The throat or pharynx composed of the nasopharynx, oropharynx and laryngopharynx (also known as hypopharynx).

More than 90% of oral cancers originate in the scaly (flat) cells that line the oral cavity. This type of cancer is identified as squamous cell carcinoma, also known as squamous cell carcinoma, an aggressive malignant tumour. This tumour is the most easily detectable with the naked eye, but also the fastest spreading tumour.

Other types of oral cancers include:

• Basal cell carcinoma, which occurs mainly on the upper lip;
• Melanoma, a skin cancer that originates in the cells that produce the pigment in the oral mucosa;
• Adenocarcinoma, which affects the salivary glands;
• Sarcoma of the bones and soft tissues of the oral cavity;
• Lymphoma;
• The teratoma;
• Other very rare malignant tumors.

Structures affected by oral cancer

Among the structures most often affected by oral cancer, there are several in the lower part of the mouth, including the tongue, the floor of the mouth (under the tongue, especially near the lingual brake and the side of the mandible on which the tongue rests) and the lower lip. Moreover, of all oral cancers, more than half are located on the sides and underside of the tongue.

In addition to the lower structures of the mouth, oral cancer also affects the soft palate and oropharynx. Very rarely, it can occur inside the cheeks (the jugal mucosa), on the gums, on the salivary glands and on the hard palate.

It is important to see a dentist promptly if you notice a change in the appearance of your mouth, whether it is a change in the size, colour or texture of the tissues or if new sensations appear, as described below. These changes may hide abnormal cell growth that can lead to cancer. That being said, these signs and symptoms do not necessarily indicate the presence of cancer, especially if they are transient, but it is better to consult if they last more than two weeks.

• Unexplained and often painless wounds or sores (ulcers or chronic lesions) inside the mouth or on the lips that bleed and/or persist for more than two weeks;
• A mass, growth or swelling in the mouth, tongue, throat or lips;
• A thick white plaque (leukoplakia) or a dark red plaque (erythroplasia) that is non-removable and more or less extensive and can be found on the tongue, gums or lips. This type of plaque can also be both white and red, and is called erythroleucoplasia.

Other signs and symptoms of oral cancer

• A feeling of numbness or persistent pain in the mouth, tongue or lips that may even radiate to the face;
• A feeling of having a thicker cheek, or part of it;
• An earache (otalgia) that persists despite the absence of signs or symptoms of other diseases, such as mumps, ear infections or nasal and sinus congestion;
• Swelling in one or more parts of the mouth and surrounding structures, such as salivary glands (especially those under the tongue), lymph nodes in the neck or upper or lower jaw;
• Gingival bleeding that is not associated with periodontal disease;
• A different feeling of the tongue when speaking and eating and/or difficulty pronouncing words in the absence of neurological disease;
• A change in voice or a feeling of always having a discomfort in the throat;
• Moving teeth or poorly fitted dentures, without signs of periodontal disease, such as gingivitis or loosening of the teeth;
• Altered taste and difficulty swallowing, in the absence of other symptoms of respiratory diseases, such as colds or flu.

Late signs and symptoms

Vigilance is required for all signs and symptoms below, as if they are associated with oral cancer, the disease may be at an advanced stage. These signs and symptoms tend to appear when the cancerous tumour grows or migrates to another part of the body to produce metastases.

It is therefore very important to consult a dentist or doctor as soon as possible in their presence, especially if early signs or symptoms, as described in the previous section, have appeared in advance and last more than two weeks:

• Severe and persistent pain or burning in the mouth;
• Swelling of the neck;
• Inability to open the mouth as much as usual;
• Difficulty or pain when swallowing or chewing;
• Difficulty moving the tongue or lower jaw;

Some of the later signs and symptoms include

• Persistent loss of appetite or weight loss that cannot be explained by physical training or a change in eating habits (diet, etc.)
• In rare cases of cancer of the oral cavity, especially when the cancer is advanced, a “hole” can form on the cheeks by a tumor lesion that comes from inside the mouth. A jaw fracture can also occur when the cancer weakens the jaw bone too much.

Reference: Canadian Cancer Society

Many cases of oral cancer originate directly in the mouth when one or more of the risk factors described below are present.

Some others originate elsewhere in the body, for example in the nasal cavity or sinuses, and spread to the mouth as metastases.

Conversely, a cancer located on the tongue or oral floor often and quickly produces distant metastases, i.e. it spreads to other parts of the body. Among those areas particularly at risk of being affected are the lymph nodes in the neck.

Like all other types of cancer, several factors (lifestyle, conditions or substances consumed) increase the risk of developing oral cancers. In addition, when some are combined, the percentage risk of developing oral cancer is even higher. Fortunately, many of them can be avoided.

The following factors have been repeatedly cited in many studies and statistics as significantly increasing the risk of developing oral cancer.

The main causes of oral cancer cases: tobacco and alcohol

Tobacco and alcohol alone are believed to be responsible for about three-quarters (75%) of oral cancers and pharynx (throat) cases. These are the most important factors and also those that can be relatively easily controlled.

• Tobacco: Tobacco, in all its forms (cigarettes, snuff, chewing tobacco, cigars, pipes, etc.), is the most important risk factor for oral cancer. The risk increases with heavy tobacco consumption over a long period of time. All anatomical structures (lips, gums, inside the cheeks, tongue, pharynx, etc.) that may come into contact with tobacco smoke or smokeless tobacco are at risk of developing precancerous and cancerous lesions.

• Frequent and/or excessive alcohol consumption: Frequent and/or excessive consumption of alcohol in all its forms (spirits, red wine, white wine, beer, etc.), especially over a long period of time, is a significant risk factor. Studies show that smoking and alcohol consumption combined constitute an explosive combination in terms of oral cancer risk. Some studies even suggest that the two substances taken together can increase the risk by about 30 times.

Other risk factors for oral cancer

The following risk factors are often responsible for one-quarter (25%) of oral cancers that are not related to tobacco and/or alcohol consumption.

• Some chews: Betel, peanut and areca nut, very popular in some countries in Asia and the Middle East, such as India and Pakistan;
• A history of precancerous conditions, such as aleukoplakia, erythroplasia, erythroleucoplakia, or oral submucosal fibrosis (scar tissue attributed to betel nut chewing). Not all of them necessarily develop into oral cancer, but the risk is still increased in their presence;
• The chronic condition called lichen planus and the appearance of ulcers inside the mouth, especially if they remain untreated for a long time;
• A diet low in fruit and vegetables. The protection that these foods provide against oral cancer comes, according to some studies, from the carotenoids of which they are composed;
• Human papillomavirus (HPV), particularly HPV-16 and HPV-18 strains, when contracted as a result of oral sex practices with a partner who has been infected through previous sexual contact. The most vulnerable anatomical structures to HPV are the root (base) of the tongue in the back of the mouth, tonsils, soft palate and oropharynx. A lesion or discoloration affecting these parts of the body is not directly visible and cannot be detected as easily by a patient with it as it is for other parts of the oral cavity, such as the gums, front of the tongue and lips;
• Sun and ultraviolet (UV) rays, especially if lips are exposed regularly and over a long period of time without adequate protection (e. g. with a lip balm containing an SPF of at least 15);
• A weakened or compromised immune system after taking certain drugs, an organ transplant, a disease or a graft-versus-host disease (GVH) following a stem cell transplant;
• A history of other cancers, in particular another oral cancer, but also other cancers affecting structures located near the mouth, such as the larynx, oesophagus and lungs, as well as cervical cancer in women;
• Some genetic predispositions, especially when a parent, sibling or child has already suffered from squamous cell carcinoma in the oral cavity;
• Predisposition by age (people over 45 years of age are at higher risk, with a higher risk after age 60), gender (men are generally twice as affected as women) and race (men of African origin are more affected by the disease). In addition, black men have a 5-year survival rate of only 33% for this type of cancer.

Other possible risk factors

Some risk factors have not yet been supported by a sufficient number of evidence-based studies, but a link has been made between them and oral cancer. The main ones are listed below.

• Second-hand smoke among non-smokers;
• Poor oral hygiene or poor dental condition. In addition to a possible risk of developing cancer, these two conditions can lead to serious dental or periodontal problems and must be taken seriously;
• The consumption of very hot foods, such as mate, frequently produces products that are consumed in South America, among others, or spicy dishes;
• Inadequate fit of partial or complete dentures, causing friction inside the mouth and which can lead to irritation and the creation of various lesions;
• Socio-economic factors, such as low wages and education.

Oral cancer remains unknown today. However, people with it can never forget it, because it touches an area of the body, the mouth, which is frequently used for eating, talking and even kissing. Oral cancer can therefore significantly reduce the quality of life of the person suffering from it, as it often brings its share of problems depending on the part of the mouth affected.

Problems directly related to cancer include dry mouth, pain or discomfort during chewing, swallowing and speaking, and even alteration or total loss of taste and sometimes smell.

Personal and social problems can also accompany physical conditions, including embarrassment in public or in communicating with others when external anatomical structures are affected by cancer. Some people with cancer can also suffer significant financial losses if the disease forces them to leave their jobs or take early retirement.

The treatment recommendation will be provided by a cancer oncologist. It will depend on the stage of the disease, the location and size of the tumour, the effects of the treatment on the patient’s condition and the overall health of the person with the disease.

Depending on all these factors, the oncologist may recommend surgery, radiotherapy and/or chemotherapy.

Since many risk factors for oral cancer are uncontrollable, it is recommended to modify certain lifestyle habits related to conditions that can be controlled in order to minimize the risk of contracting the disease.

Some recommendations may apply, including

• Stopping the consumption of tobacco products;
• The cessation of the combined consumption of tobacco products and alcohol;
• Moderate alcohol consumption;
• Maintaining a healthy lifestyle;
• Maintaining good oral hygiene measures.

Finally, it is strongly recommended to make an appointment once or twice a year with your dentist for a cleaning (prophylaxis) and a complete oral examination. This examination makes it possible to act as a preventive measure when problems, some of which are more serious, such as cancerous tumours, appear.