Is a Sore That Won't Heal a Sign of Cancer?

This page is for anyone with a sore on the skin or in the mouth that will not heal. It explains how long to wait, what else can slow healing, and which signs are urgent.

Skin and mouth have different clocks. Mixing them up is the most common mistake here.

For skin, the American Cancer Society says to see a health care provider about new or changing skin growths and sores that don't heal. It gives no set number of weeks. The NHS (the UK's National Health Service) also lists a growth that is getting bigger or has changed color or texture.

For the mouth, the number is 3 weeks. MedlinePlus says to see a provider if a mouth ulcer does not go away after 3 weeks, or if ulcers keep coming back. The American Cancer Society adds a white or red patch inside the mouth that lasts more than a few weeks.

Both mean book an appointment with your primary care doctor or dentist. Neither is a reason to go to the emergency room.

Some sores never quite finish. They scab, look settled for a week, then break down in the same spot.

That pattern is worth describing in exactly those words when you book. It is different from a wound that is slowly shrinking. The American Cancer Society describes skin cancer sores that heal and then come back.

Take a photo the first time it opens. If it reopens, you will have proof it is the same place rather than a new knock.

The NHS says the main symptom of non-melanoma skin cancer is a growth or unusual patch on the skin. It is most common in areas exposed to the sun:

• the head, face and ears
• the neck and shoulders
• the back
• the hands
• the lower legs

It describes the range these can take. Some growths are raised and smooth with clear edges. Some are bumpier, rough or crusty. Some start as a flat discolored patch. Colors can include purple, brown and red, which may look darker on brown or black skin.

That variety is the point. There is no single look to memorize.

Cancer is not the usual reason a sore lingers.

Pressure keeps reopening skin over a heel, a hip or the base of the spine. Poor circulation starves a leg ulcer of what it needs to heal. Diabetes slows healing and can dull the pain that would normally make you shift position. Infection stalls a wound. Eczema, psoriasis and repeated scratching can keep a patch raw for months. Steroids and some other medicines thin the skin.

Most of these have treatments. That is another reason to have it looked at rather than covered up.

NCI lists a sore on the lip or in the mouth that does not heal among lip and oral cavity cancer symptoms. The rest of its list is:

• a lump or thickening on the lips, gums or in the mouth
• a white or red patch
• bleeding, pain or numbness in the lip or mouth
• a change in voice
• loose teeth or dentures that no longer fit
• trouble chewing, swallowing or moving the tongue or jaw
• jaw swelling
• a sore throat or a feeling of something caught

NCI adds that these cancers may cause no symptoms at all, and are sometimes found during a regular dental exam. A dentist is a reasonable first stop.

Infection is the one thing here that changes within hours.

An infection can turn into sepsis, which the CDC calls a medical emergency. Its signs include a fast heart rate or weak pulse, fever, shivering or feeling very cold, confusion, shortness of breath, extreme pain, and clammy or sweaty skin. If these come with an infected sore, call 911 or go to the emergency room.

Otherwise, book. Our page on preparing for appointments explains what to bring.

• NHS — Symptoms of non-melanoma skin cancer
• NHS — Symptoms of mouth cancer
• NHS — Sepsis
• American Cancer Society — Signs and Symptoms of Basal Cell Carcinoma
• American Cancer Society — Signs and Symptoms of Oral Cavity and Oropharyngeal Cancer
• MedlinePlus — Mouth ulcers
• CDC — Protect yourself and your family from sepsis
• National Cancer Institute — Lip and Oral Cavity Cancer Treatment (PDQ)