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This article cannot tell you whether a change in your mouth is cancer. It describes the recognised warning signs so you know which ones warrant examination, and how soon. The single most reliable rule is a threshold of time: most warning signs of mouth cancer are changes that do not settle within two to three weeks. If you have any of the signs below and they have lasted that long, book an appointment with an oral medicine specialist, your dentist, or your doctor — and do not rely on any article for a diagnosis.
Mouth cancer (oral cancer) is a malignant growth, most commonly an oral squamous cell carcinoma, that can arise on the lips, tongue, floor of the mouth, gums, inner cheeks, or palate. It often begins as a small, painless change that is easy to dismiss — which is exactly why knowing the warning signs matters.
What are the warning signs of mouth cancer?
The signs and symptoms that should prompt a clinical examination, particularly when they persist beyond two to three weeks, are:
- A sore or ulcer that does not heal. A typical mouth ulcer heals within 10 to 14 days. An ulcer still present after two to three weeks, with no obvious cause, is the most consistently emphasised warning sign — the NICE referral guidance uses an unexplained oral ulceration lasting more than three weeks as a threshold for referral (NICE NG12).2
- A red patch (erythroplakia) or white patch (leukoplakia) that cannot be wiped off. These are potentially malignant disorders of the oral mucosa; erythroplakia in particular carries a meaningful risk of malignant change (Warnakulasuriya, 2018).3
- A lump or thickening anywhere in the mouth, on the lip, or in the cheek.
- Persistent pain or numbness in the mouth, lip, or tongue that has no dental explanation.
- Difficulty or discomfort swallowing, or a persistent sensation of something caught in the throat.
- A loose tooth, or teeth, with no dental cause — loosening not explained by gum disease or trauma.
- A lump in the neck (an enlarged lymph node) that persists.
- A patch of numbness, persistent hoarseness, or an area that bleeds easily when touched.
No single sign confirms cancer, and each of these has common, benign explanations far more often than not. The point is not to alarm — it is that these are the changes that cannot be safely assumed harmless from appearance alone. They can develop anywhere in the mouth, but the lateral (side) and underside surfaces of the tongue, the floor of the mouth, the soft palate, and the lower lip are recognised higher-risk sites and warrant a lower threshold for examination.
What raises the risk of mouth cancer?
Mouth cancer is strongly linked to specific exposures, and most cases occur in people with one or more of them:
- Tobacco in any form — cigarettes, cigars, pipes, and smokeless tobacco (snuff, chewing tobacco). This is the strongest modifiable risk factor.
- Alcohol — heavy use raises risk, and alcohol combined with tobacco multiplies risk rather than simply adding it.
- Betel quid and areca ("betel") nut — areca nut is classified by the IARC as a Group 1 (established) human carcinogen (IARC / WHO).4
- HPV infection — predominantly relevant to cancers at the back of the throat (oropharynx).
- Heavy sun exposure — a leading risk factor specifically for cancer of the lip.
- A previous oral cancer or a potentially malignant lesion — these require lifelong surveillance.
Cancer of the lip and oral cavity accounted for an estimated 377,713 new cases worldwide in 2020 (GLOBOCAN), with the burden concentrated in tobacco- and alcohol-using populations.5 In South Africa, smoked and smokeless tobacco and alcohol are the leading modifiable risk factors. A person with none of these exposures can still develop oral cancer, so the warning signs apply to everyone.
Why does early detection matter so much?
Stage at detection is the single biggest driver of outcome in mouth cancer. Oral-cavity cancer found at a localised stage has a 5-year relative survival of about 89%, falling to about 38% once it has spread to distant sites (NCI SEER).1 That difference is the reason a non-healing sore is worth a two-week look rather than a "wait and see" — early lesions are small, easier to treat, and far more survivable. For any single persistent sore or patch, cancer is not the likely cause; trauma, aphthous ulcers, infection, and benign mucosal conditions are all more common. The threshold is set at two to three weeks not because cancer is probable, but because it is the diagnosis where early detection most changes the outcome and cannot be ruled out by appearance.
Common questions
How long is too long for a mouth ulcer or sore? Most ulcers heal within 10 to 14 days. A sore that has not healed after two to three weeks, with no obvious cause, should be examined. NICE referral guidance treats an unexplained oral ulceration lasting more than three weeks as a threshold for referral (NICE NG12).2
Is mouth cancer painful? Often not in its early stages. Oral cancers are frequently less painful than benign ulcers of similar size, so the absence of pain is not reassurance. A painless lesion that persists still warrants examination.
Can a dentist or specialist tell if it is cancer just by looking? No. Examination narrows the possibilities and identifies which lesions are suspicious, but a definitive diagnosis requires a biopsy — a small tissue sample examined by an oral pathologist. Most biopsies of oral lesions return benign results.
I have no risk factors. Should I still be concerned about a persistent change? Yes. Tobacco, alcohol, and areca nut raise risk, but oral cancer also occurs in people with none of these. A change that persists beyond two to three weeks should be examined regardless of risk profile.
What to do next
Within oral medicine, both Dr Leande Kotze and Dr Christa Blignaut perform clinical oral cancer screening, surveillance of potentially malignant lesions, and biopsy when indicated. If you have a sign described here that has lasted more than two to three weeks, take a photograph for comparison, note when it appeared, and book an appointment.
This article is general educational content. The cause of any specific change in your mouth can only be established by a clinical examination, sometimes supplemented by biopsy — a consultation gives you a clinical answer for your individual situation.