Cancer prognosis is generally better the earlier the disease is caught, with treatment able to start quickly in order to minimise and reverse the damage.
But some cancers can have 'silent' symptoms, meaning they don't show typical signs you may associate with a serious illness.
Spotting these symptoms could help your doctor find the cause of a serious conditions much quicker.
Dr Alexandra Oliver, associate clinical director at Bupa Health Clinics (bupa.co.uk), told The Independent : “Many people are aware of the obvious signs of cancer, such as a new lump or a change to a mole.
"However, other symptoms may be less obvious, but it’s still important that people are aware of them.
“In most cases, it’s likely to be nothing serious, but making sure you get checked out by a doctor if you have any symptoms, particularly persistent ones, is essential."
Here are seven of the less obvious possible signs of cancer.
Fatigue
It's perfectly normal to feel tired sometimes, and usually having a good night's sleep is enough to energise you. But Dr Oliver said that if you constantly feel tired and there isn't anything obvious causing it, it's worth mentioning it to your GP.
Night sweats
Night sweats are pretty common and can, for example, affect people taking certain antidepressants or women on their period or going through the menopause. However, Dr Oliver said some cancers such as bone cancer, leukemia and liver cancer can also be associated with persistent night sweats.
Persistent indigestion and heartburn
Indigestion and heartburn often happen after eating certain types of food, such as high fat dishes or if a person is overweight, smokes or is pregnant.
Dr Oliver said, however, that if you're experiencing persistent, regular acid reflux it might be due to gastroesophageal reflux disease, a hiatus hernia, oesophageal cancer or stomach cancer.
She recommends speaking to a doctor if this happens.
Long-lasting mouth ulcers
Lots of people get mouth ulcers that can be painful but usually go away on their own.
They tend to be caused by poorly fitted dentures, erupting wisdom teeth, medication, infections, dietary deficiencies or damage caused by brushing. But dentist Susie Lloyd, from Bupa Dental Care, said if a mouth ulcer hasn't healed after three weeks you should seek help as it could be mouth cancer.
Persistent hoarseness
Hoarseness can be caused by a dry or sore throat or overusing your voice.
However, Dr Oliver said that if it lasts 10 days or more speak to your GP, as there's a chance it could be a serious underlying medical condition, such as laryngeal cancer.
Persistent bloating
Bloating, like indigestion and heart burn, is very common and often down to what you've eaten, especially if you have a condition such as irritable bowl syndrome (IBS).
But there is a small chance bloating is a sign of gynaecological or bowel cancer. If you start to feel persistently bloated and haven't before, visit your doctor.
You can find out more about cancer symptoms on the NHS website.
Persistent cough
Coughs are very normal and tend to go away on their own within three weeks. But if you have a cough that persists longer than this, go see your GP said Dr Oliver, as there's a small chance it's lung cancer.
