There are hundreds of different types of cancer - 200 in total - that exhibit common symptoms, but more unusual signs can typically be missed.
Many cancers share signs that can be spotted easily, like weight loss, tiredness, and painful lumps, reports MyLondon.
However, some cancers produce symptoms inside the mouth, and these would requite a trip to your local GP surgery.
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And while cancer signs can be different for every individual, it is important to be aware what is normal for you, and what is unusual - and to tell your doctor if you spot any changes.
Doing this can help doctors diagnose cancer at earlier stages, when treatment is more likely to be successful.
Two of the biggest red flags in the mouth that could indicate cancer are persistent ulcers, and problems swallowing food or drink.
Cancer Research UK has warned anyone having difficulty swallowing to see their GP immediately. Ulcers in the mouth are common, and can appear when a person is run down - but they tend to heal on their own within three weeks.
However, if you spot an ulcer with a red or white patch that is lasting longer than three weeks, you should look into getting a doctor or dentists appointment.
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Common cancer signs can include fevers or heavy night sweats, which can also be caused by infections or a side effect of certain medications.
People should speak to their GP in the first instance if they are experiencing severe night sweats or an unexplained fever.
Unexplained bleeding or bruising, including blood in your poo or pee as well as vomiting or coughing up blood, should also be mentioned to a doctor.
Also, aches and pains that are unusual and cannot be explained anywhere in the body could also be a sign of cancer, and need to be examined further.
Other cancer symptoms include: fatigue, unexplained weight loss and persistent lumps or swelling in any part of your body.
Lumps can form in the neck, armpit, groin, stomach, breast, chest or testicle, and other signs of cancer that affect individual parts of the body can be found on the Cancer Research website.
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