Oral cancer: signs to watch for

Reviewed by Dr. Samar Fadavi, DDS

Short answer: Oral cancer can start on the tongue, gums, cheeks, lips, floor or roof of the mouth, or the throat. Warning signs include a sore that does not heal within two weeks, a red or white patch, a lump, numbness, or trouble swallowing. Most mouth sores are harmless, but anything that lasts beyond two weeks should be checked by a dentist or doctor.

What are the signs of oral cancer, and what should you watch for?

Oral cancer is not as widely discussed as some other cancers, but it is a serious disease, and it is far easier to treat when found early. The difficulty is that early oral cancer is often not painful. It can look like an ordinary ulcer, a small patch or a rough spot that a person gets used to. That is why a careful look at the soft tissues of the mouth is part of every dental check-up, and why it helps to know what to watch for yourself.

This guide explains where oral cancer can develop, the warning signs, the main risk factors, how a screening works, and how to check your own mouth. It is general information, not a diagnosis. If something in your mouth worries you, please have it looked at.

Where oral cancer develops

The term oral cancer usually covers cancers of the lips, tongue, gums, inner cheeks, floor of the mouth under the tongue, and the hard palate (the roof of the mouth). Cancers of the oropharynx, the part of the throat at the back of the mouth that includes the base of the tongue, the soft palate and the tonsils, are closely related and are often discussed together.

Most oral cancers begin in the thin, flat cells that line the mouth. Some start as a precancerous change, an area of abnormal cells that is not yet cancer but may become cancer over time. Finding and monitoring these changes is one of the main goals of a screening.

Warning signs to watch for

See a dentist or doctor if any of the following lasts longer than two weeks:

• A sore or ulcer in the mouth or on the lip that does not heal.
• A white patch (leukoplakia) or red patch (erythroplakia) on the gums, tongue, cheek, floor or roof of the mouth. Red patches are less common but more concerning.
• A lump, thickening or rough area in the mouth, on the lip or in the neck.
• Bleeding in the mouth without a clear cause.
• Numbness, tingling or loss of feeling in the tongue, lip or another part of the mouth.
• Pain or difficulty chewing, swallowing or moving the tongue or jaw.
• A feeling that something is caught in the throat.
• A change in voice or ongoing hoarseness.
• A tooth that becomes loose without gum disease, or dentures that suddenly stop fitting.
• Ear pain on one side without an ear problem.
• Unexplained weight loss.

Most of these signs turn out to have a harmless cause, such as a bite injury, an irritation from a sharp tooth or denture, a fungal infection or a canker sore. The two-week rule is useful: an ordinary sore usually heals within that time once the cause is removed. Anything that does not should be checked.

Risk factors

Anyone can develop oral cancer, including people with none of the risk factors below, but some things raise the risk:

• Tobacco in any form. Cigarettes, cigars, pipes, chewing tobacco, snuff and waterpipe (hookah) use all raise the risk significantly.
• Alcohol. Regular heavy drinking raises the risk, and tobacco and alcohol together raise it far more than either alone.
• Human papillomavirus (HPV). Certain types of HPV are linked with cancers of the oropharynx, at the back of the mouth and throat. These cancers have been increasing, including in younger adults who do not smoke. HPV vaccination is offered through school programs in Ontario.
• Betel quid, areca nut and gutka. Chewing these, a practice in some South Asian and other communities, is strongly linked with oral cancer.
• Sun exposure. Long-term sun exposure raises the risk of lip cancer, especially on the lower lip.
• Age. Risk increases with age, though it can occur at any age.
• A weakened immune system. For example after an organ transplant.
• A previous oral cancer or precancerous change.
• Diet. Diets low in fruit and vegetables have been linked with higher risk.

How an oral cancer screening works

An oral cancer screening is a quick, gentle examination done as part of a regular check-up. It takes a few minutes and needs no special preparation.

1. Questions about your health and habits. The dentist asks about tobacco, alcohol, medications and any changes you have noticed.
2. Looking at the face and neck. The dentist checks for swelling, lumps or changes in the skin.
3. Feeling the neck and jaw. Gentle pressure along the neck and under the jaw checks the lymph nodes.
4. Checking the lips. Inside and outside, for colour changes, lumps or sores.
5. Checking the cheeks and gums. Using a small mirror and light.
6. Checking the tongue. You stick your tongue out, and the dentist holds it gently with gauze to see the sides and underneath, the most common sites for oral cancer.
7. Checking the floor and roof of the mouth. Including feeling for lumps under the tongue.
8. Checking the back of the throat. As far as can be seen.

If something unusual is found, the dentist may remove a possible cause, such as smoothing a sharp tooth or adjusting a denture, and ask you to return in two weeks. If an area is still present or looks concerning, you may be referred for a biopsy, a small sample of tissue examined in a laboratory. Being referred does not mean you have cancer. Most biopsies show a harmless cause, and those that do not are found at a stage where treatment has more options.

How to check your own mouth, step by step

A monthly self-check takes about two minutes. Use a mirror in good light, and remove any dentures first.

1. Face and neck. Look for swelling or lumps on either side. Feel gently along both sides of your neck and under your jaw.
2. Lips. Pull your lower lip down and your upper lip up. Look for sores or colour changes and feel for lumps.
3. Cheeks. Pull each cheek out and look at the inside. Feel the cheek between your thumb and finger.
4. Gums. Look along the gums, top and bottom, front and back.
5. Tongue. Stick your tongue out and look at the top. Hold it with a clean cloth and move it to each side to see the edges. Lift it to the roof of your mouth to see underneath.
6. Floor of the mouth. With your tongue lifted, look and gently feel under it.
7. Roof of the mouth. Tilt your head back and look up.

Note anything new. If it is still there after two weeks, book an exam.

Lowering your risk

• Avoid tobacco in all forms. If you smoke or chew tobacco, ask your doctor or pharmacist about support to quit. The risk falls over time after stopping.
• Limit alcohol. Follow Canada’s guidance on alcohol and health.
• Avoid betel quid, areca nut and gutka.
• Protect your lips from the sun. Use a lip balm with SPF and wear a wide-brimmed hat outdoors.
• Talk to your doctor about HPV vaccination if you or your children have not had it.
• Eat plenty of fruit and vegetables.
• Keep dentures well fitted. A denture that rubs constantly should be adjusted.
• Keep regular check-ups, including after you have lost your natural teeth.

What to avoid

• Waiting for pain. Early oral cancer is often not painful.
• Treating a lasting sore with home remedies for weeks. If it has not healed in two weeks, have it checked.
• Assuming you are too young. HPV-related cancers can affect adults in their thirties and forties who have never smoked.
• Skipping check-ups because you wear dentures. The soft tissues still need to be examined.
• Feeling embarrassed to ask. Dentists look at mouth sores every day. Asking is always the right call.

Living with risk: practical support

Knowing your risk factors is useful only if it leads to action that fits your life. If you smoke and want to stop, your family doctor or pharmacist can talk you through nicotine replacement and other supports, and Ontario offers telephone and online quit programs. If you drink most days, small steps such as a few days each week without alcohol can reduce your exposure over time. If betel quid or areca nut is part of family or cultural routine, talking with your doctor about the risks can be a first step for the whole household.

If you have had a precancerous change or an oral cancer in the past, regular checks are especially important. Treatment for head and neck cancer, including radiation, can also leave lasting effects in the mouth, such as dry mouth, stiffness of the jaw and a higher risk of decay. Dentists work alongside cancer care teams to protect teeth before, during and after treatment. Fluoride trays, saliva substitutes, gentle cleaning and careful monitoring all help.

For people supporting an older parent or a family member with limited mobility, a look inside their mouth during daily care can spot changes early. A torch, a soft toothbrush and a few calm minutes are all it takes. Mention anything you notice at their next visit.

Dental care before and during cancer treatment

People treated for head and neck cancer often need a dental check before radiation or chemotherapy begins, so that infected or broken teeth can be dealt with first. During treatment, the mouth can become dry and sore. Gentle brushing with a soft brush, bland rinses recommended by the care team, and fluoride as advised all help protect the teeth. After radiation to the jaw, extractions need careful planning, so regular check-ups and early treatment of small problems are especially important. Your dentist works with your oncology team throughout.

When to see a dentist

• Any sore, patch, lump or numbness in the mouth that lasts longer than two weeks.
• Difficulty swallowing, chewing or moving your tongue that does not go away.
• A lump in your neck.
• Dentures that suddenly stop fitting, or a tooth that loosens without a clear reason.
• It has been more than a year since your last check-up, especially if you smoke or drink alcohol regularly.

An oral cancer screening is part of every check-up at our office. Our check-ups and family dentistry page explains what a routine visit includes, and our page on dental care for seniors describes how we care for older adults, including those with dentures.

Questions about oral cancer

Is a canker sore a sign of cancer?

Canker sores are very common and are not cancer. They are usually painful, round with a red border, and heal within one to two weeks. A sore that is not painful, has hard edges or does not heal in two weeks should be checked.

What does a white patch in the mouth mean?

White patches have many causes, including friction from a sharp tooth, cheek biting and fungal infection. A white patch that cannot be wiped away and does not have a clear cause should be examined, as some can be precancerous.

Does a screening hurt?

No. It is a visual and gentle hands-on examination that takes a few minutes.

Can non-smokers get oral cancer?

Yes. HPV-related cancers of the throat and base of the tongue often affect people who have never smoked.

How often should I be screened?

A screening is done as part of regular check-ups. If you have higher risk factors or a past precancerous change, the dentist may suggest more frequent checks.

What happens if I am referred for a biopsy?

A small piece of tissue is removed under local anaesthetic and examined in a laboratory. Most results show a harmless cause. If not, early findings usually mean more treatment options.

Do I still need screening if I have no teeth?

Yes. Oral cancer affects the soft tissues, not the teeth, so people with dentures still benefit from regular checks.

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