Canker Sore vs. Cancer: What Are the Differences?

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A mouth sore can be irritating and, at times, concerning. A common canker sore and an oral cancerous lesion can seem similar at first glance. Both form an ulcer inside the mouth. While you may be fairly sure that you have a canker sore, you may have a lingering doubt.

The good news is there are ways to distinguish these two sores. A lesion that's red and painful early on is usually a canker sore. Oral cancer often is not painful at first.

A typical canker sore is flat and will heal with time. If there is a bump under the lesion or the sore does not get better after a few weeks, it may be something else. See a healthcare provider to identify the lesion and ensure you get the correct treatment.

This article will discuss what distinguishes canker sores from oral cancer. Learn more about the symptoms, causes, diagnosis, treatment, and preventive measures of sores in the mouth.

Healthcare provider looks into a person's mouth

stefanamer / Getty Images


Both canker sores and oral cancer can appear as an ulcer in the mouth. These lesions may appear on the cheeks, lips, or on or under the tongue. The location alone cannot tell which type of lesion you may have. But some differences can help to distinguish between the two.

Canker Sore Symptoms vs. Oral Cancer

Canker Sore
  • Is often painful

  • Is often red and inflamed around the edges

  • Is often flat

  • Usually heals on its own within two to three weeks

Oral Cancer
  • Not usually painful in the early stages, but later may have persistent pain

  • Has white or red patches

  • May cause a bump

  • Is a persistent lesion that may get worse over time

Some symptoms that may occur with oral cancer include difficulty chewing, talking, or moving the jaw or tongue. You might have an area of numbness in the mouth. You may experience lumps or swelling in the neck, cheek, or jaw, or you may have changes in your teeth or how your dentures fit.


The causes of canker sores and oral cancer are very different.

Canker Sore

No one knows for sure what causes a canker sore. Canker sores might be caused by an allergic reaction (in which the immune system reacts to what it perceives as a foreign substance) or an autoimmune reaction (in which the immune system attacks the body's own tissues).

The formation of a canker sore can be triggered by an injury or irritation in the mouth. Other potential triggers include smoking, stress, and nutritional deficiencies such as low levels of vitamin B12, folic acid, or iron. In some cases, the onset of menstruation can trigger a canker sore.

Oral Cancer

Oral cancer has a variety of causes. Oral cancer can be caused by tobacco use (in any form) or heavy alcohol use. A human papillomavirus (HPV) infection, specifically HPV 16, can lead to oral cancer. Risk factors include sun exposure (especially for oral cancer on the lip) and age, with oral cancer usually occurring in people over age 40.


People generally determine they have a canker sore by its symptoms and how it develops, and often do not seek a diagnosis from a healthcare provider. But when you have a mouth sore that varies from the usual pattern of canker sore symptoms, consider seeing a healthcare provider.

Canker Sore

People generally determine they have a canker sore by its symptoms and how it develops, and often do not seek a diagnosis from a healthcare provider. But when you have a mouth sore that varies from the usual pattern of canker sore symptoms, it is wise to see a healthcare provider.

If a mouth sore hasn't healed after a couple of weeks or if it becomes even more inflamed, see your primary care provider or dentist to ensure the sore isn't due to a different condition.

Expect a medical provider to look closely at the pink lining of your mouth and ask if you have noticed any other signs that something is amiss.

To identify a cause and determine if your sore is related to a disease, your provider may swab the area, perform a blood test, or take a sample from the area to be tested in a lab.

Oral Cancer

If you suspect a lesion may be oral cancer, it should be promptly checked by a dentist or other healthcare provider. During the exam, they will visually examine the lesion and the inside of your mouth for any other worrisome signs. They will also feel around your neck, looking for any swollen glands.

The examination might also use special mirrors or fiberoptic scopes to look into your mouth and throat. If the healthcare provider is concerned the lesion may be cancerous, they may refer you to an oncologist (cancer specialist).

You can expect to have a biopsy, in which a sample is taken from the lesion to analyze in the lab. This may determine whether cancer is present. The sample may also be tested for HPV.

Imaging may also be performed before or after diagnosis, depending on symptoms and the possible spread of cancer.


While canker sores will usually get better without treatment, oral cancer must be treated as soon as possible.

Canker Sore

If you are uncomfortable, use a saltwater rinse or apply over-the-counter (OTC) gels, ointments, or mouthwashes with medication to ease the pain. In severe cases, a healthcare provider or dentist will recommend treatment to soothe symptoms.

Oral Cancer

The treatment you will receive for oral cancer will depend on how early it is detected, the size of the tumor, the type of cancer, and whether it is still confined to a local area.

In cases in which oral cancer is found early, you will need to undergo surgery or receive radiation treatment. If the tumor is more advanced, you may need to undergo a combination of these treatments. Another possibility may be targeted therapy, where treatment is aimed at specific characteristics of the tumor.


You can lower the risk of developing a canker sore or oral cancer by taking precautions.

Canker Sore

To keep canker sores at bay, avoid common triggers. Steps you can take include:

  • Keep your mouth as clean as possible by thoroughly brushing and flossing after meals.
  • Use a soft toothbrush to avoid irritating your gums.
  • If you wear braces, cover any sharp edges with wax.
  • Keep calm and avoid stress.
  • Stay away from any foods that you notice tend to trigger a canker sore outbreak.

Oral Cancer

You can reduce your risk of oral cancer by doing the following:

  • Do not use any form of tobacco.
  • Avoid heavy alcohol use.
  • Do not use alcohol if you smoke, and vice versa, as the combination increases the risk of oral cancer.
  • Lower your risk of HPV infection by getting the HPV vaccine (ideally between ages 11 and 12). Also, be aware that oral sex or having multiple partners can increase the likelihood of oral HPV infection; smoking further increases risk.
  • Keep exposure to ultraviolet (UV) light minimal. Use sunscreen and lip balm with a sun protection factor (SPF) of at least 30. Wear a hat to shade your face from sunlight.
  • Eat a balanced diet and maintain a healthy weight.
  • Get regular dental checkups to catch any precancerous growths early.


Both canker sores and oral cancer are lesions that appear in the mouth and may look similar at first. In the early stages, canker sores tend to be painful and red, while early oral cancer is often painless. The canker sore also tends to be flat, while oral cancer may have a bump. Canker sores resolve quickly on their own, while oral cancer does not.

If you have a lesion that does not go away, it's essential to see a dentist or other healthcare provider for a diagnosis. While treatment is usually not necessary for canker sores, you may wish to rinse with saltwater or use OTC remedies to soothe symptoms. Oral cancer found early can be surgically removed or treated with radiation.

10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. University of Texas MD Anderson Cancer Center. Canker sore vs. oral cancer: how can you tell the difference?

  2. American Cancer Society. Signs and symptoms of oral cavity and oropharyngeal cancer.

  3. University of Michigan. Cold and canker sores.

  4. National Institute of Dental and Craniofacial Research. Oral cancer.

  5. Institute for Quality and Efficiency in Health Care (IQWiG). Canker sores (mouth ulcers): overview.

  6. American Cancer Society. Tests for oral cavity and oropharyngeal cancers.

  7. Mount Sinai. Canker sore.

  8. Cedars Sinai. Everything you wanted to know about canker sores.

  9. American Cancer Society. Can oral cavity and oropharyngeal cancers be prevented?

  10. Centers for Disease Control and Prevention. HPV vaccine schedule and dosing.

By Maxine Lipner
Maxine Lipner is a long-time health and medical writer with over 30 years of experience covering ophthalmology, oncology, and general health and wellness.