Lung cancer is the second most common cancer worldwide.
It takes the lives of around 34,800 people in the UK and more than 120,000 in the US each year.
Yet many are not aware of all the symptoms.
A persistent cough is just one telltale sign of the disease, but it could also be lesser-known conditions, 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 watch out for.
A persistent cough, shortness of breath, and fainting are all symptoms of lung cancer, according to Cancer Research
Dame Esther Rantzen, 82, has revealed that her lung cancer diagnosis, which she announced in January, was rated 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 doesn’t go away and often feel breathless, the NHS says.
If you feel lethargic while doing things that are normally not a problem, that’s a sign to see a doctor.
This symptom may also be accompanied by coughing up blood and pain in the shoulder or chest when coughing.
Lung cancer is rare in people under 40 and more than four in 10 people diagnosed in the UK are aged 75 and over, 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, says cancer research.
The nails may appear to ‘float’ instead of being attached to the nail bed and form a sharper angle with the cuticle.
Clubbing can also make the tip of the finger look big and red and cause the nail to bend down, resembling the round part of an upturned 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 get this symptom, and it’s more common in people with non-small cell lung cancer, says Cancer Research.
Seizures or fainting
Dizziness when standing up and fainting may be signs of cancer.
Although rare, some lung cancer patients develop a rare condition called paraneoplastic syndrome in addition to their cancer.
It is caused by tumors that release hormones into the bloodstream that cause the body’s organs and body systems to behave abnormally.
This can lead to symptoms that appear to be unrelated to lung cancer.
These include headache, vomiting, confusion, feeling tired, muscle weakness, seizures, fainting, dizziness and also constipation.
Paraneoplastic syndrome is rare, but it is more common in people with small cell lung cancer.
Hanging of one eyelid
A rare form of lung cancer that grows at the top of the organ can cause one eyelid to droop, experts say.
Pancoast tumors, which account for less than five percent of lung cancer cases, can also cause one pupil to become small.
And it can stop sweating on one side of the face, cancer research says.
Shoulder pain or pain that goes up and down the arm, neck and head are more common symptoms of this cancer, according to Cancer Research.
Lose weight
About 60 percent of people with lung cancer have significant weight loss at the time of their diagnosis, says Cancer Research.
This may be because lung cancer causes a loss of appetite.
However, some people lose weight even when they eat normally.
This is called cachexia, where your body doesn’t absorb all the fat, protein, and carbohydrates from your food and burns calories faster than normal.
Scientists say cancer releases chemicals into the blood that contribute to fat and muscle loss.