Lung cancer is the second most common cancer worldwide.
It takes the lives of around 34,800 people in the UK every year and more than 120,000 in the US.
Yet, many are not aware of all the symptoms.
A persistent cough is just one tell-tale sign of the disease, but it can also lesser-known ailments such as swollen fingers and nails.
Following TV legend Esther Rantzen’s announcement today that she has stage four lung cancer, MailOnline reveals the warning signs to look out for.
A persistent cough, breathlessness and passing out are all symptoms of lung cancer, according to Cancer Research
Dame Esther Rantzen, 82, has revealed her diagnosis with lung cancer, which she announced in January, was assessed as Stage 4
Getting out of breath
Often there are no symptoms in the early stages of lung cancer.
But many people eventually develop a persistent cough that won’t go away and often feel breathless, the NHS says.
Feeling out of puff while doing the things that usually wouldn’t be a problem is a sign to visit the GP.
This symptom may also be coupled with coughing up blood and a pain in the shoulder or chest when coughing.
Lung cancer is rare in people under the age of 40 and more than four in 10 people diagnosed in the UK are 75 and older, the NHS says.
It adds that smoking is the most common cause of lung cancer.
Swollen fingers and nails
Changes in the shape of your fingernails and swelling can be a sign of lung cancer.
This symptom is called clubbing, Cancer Research says.
The nails can appear to ‘float’ instead of being attached to the nailbed and form a sharper angle with the cuticle.
Clubbing can also cause the end of the finger to appear large and red and the nail to curve downwards, so it looks like the round part of an upside-down spoon.
The symptoms are caused by hypertrophic pulmonary osteoarthropathy (HPOA) — a condition that causes inflammation in the bones and joints and affects some people with cancer.
However, not everyone who has lung cancer will develop this symptom and it is more common among those with non-small cell lung cancer, says Cancer Research.
Seizures or passing out
Dizziness when standing up and passing out can be signs of cancer.
Although rare, some lung cancer patients develop a rare condition alongside their cancer called paraneoplastic syndrome.
It is triggered by tumours releasing hormones into the bloodstream that cause the body’s organs and body systems to behave abnormally.
This can lead to symptoms that don’t seem related to lung cancer.
These include headaches, vomiting, confusion, feeling tired, muscle weakness, seizures, passing out, dizziness and also constipation.
Paraneoplastic syndrome is rare but more common among those with small cell lung cancer.
Drooping of one eyelid
A rare type of lung cancer that grows at the top of the organ can cause one eyelid to droop, experts say.
Pancoast tumours, which account for less than five per cent of lung cancer cases, can also cause one pupil to go small.
And it may stop sweating on one side of the face, Cancer Research says.
Shoulder pain or pain that travels up and down the arm, neck and head are more common symptoms of this form of cancer, according to Cancer Research.
About 60 per cent of people with lung cancer have significant weight loss at the time of their diagnosis, Cancer Research says.
This can be because lung cancer causes a loss of appetite.
However, some people lose weight even when they are eating normally.
This is called cachexia, where your body doesn’t absorb all the fat, protein and carbohydrate from your food and burns calories faster than normal.
Scientists say cancer releases chemicals into the blood that contribute to the fat and muscle loss.