Cancer is caused by cells in a specific part of the body reproducing uncontrollably, according to the NHS.
The healthy tissue surrounding these cells can be destroyed by the cancer – including organs.
More than a third of all people will develop cancer at some point in their lifetime.
You could be at risk of mouth cancer if you have white patches on the inside of your mouth.
Having white patches in the mouth is a condition known as leukoplakia.
Leukoplakia patches often appear on the tongue, but could also be found on the inside of cheeks, or around the gums, said the NHS.
The condition is a pre-cancerous area, and should be seen by a doctor, said the American Cancer Society.
“The best way to find some cancers early, when they’re small, have not spread, and are easier to treat, is through routine screenings – tests to check for cancer before there are any symptoms of the disease,” it said.
“Knowing what symptoms to look for is complicated because cancer is not just one disease, but a group of diseases that can cause almost any sign or symptom.
“The signs and symptoms will depend on where the cancer is, how big it is, and how much it affects the organs or tissues.
“White patches inside the mouth and white spots on the tongue may be leukoplakia.
“Leukoplakia is a pre-cancerous area that’s caused by frequent irritation. It’s often caused by smoking or other tobacco use and can become mouth cancer if not treated.”
Leukoplakia patches aren’t painful, and can’t be scraped away, added the NHS.
Look out for white patches that are irregularly shaped, or are slightly raised.
Speak to a dentist or GP if you have any white patches in the mouth that haven’t gone away after two weeks.
Mouth cancer, or oral cancer, can develop on the surface of the tongue, the inside of cheeks, or on the roof of the mouth. It could also be spotted on the lips or the gums.
Mouth cancer symptoms include sore ulcers that won’t heal, having unexplained lumps in the mouth, or unexplained loose teeth.
It’s the sixth most common cancer in the world, and almost 7,000 people are diagnosed with the condition in the UK every year.
Most cases are diagnosed in older adults, between the ages of 50 and 74.
Men are also more at risk than women – possibly because men tend to drink more alcohol than women, the NHS added.