Scientists have identified a genetic mutation which makes lung cancer more aggressive and increases the risk of the disease spreading.
The LKB1 gene is a 'master gene' which, previous studies have suggested, prevents cells becoming cancerous.
US researchers from Dana-Farber, Massachusetts General Hospital and the University of North Carolina School of Medicine found that mutated versions of the gene seem unable to fulfil this function.
The mutation occurs spontaneously and affects approximately 30 per cent of lung cancer cases, according to the study which appears in this month's edition of Nature.
Kwok-Kin Wong, the study's senior author, said: "We're currently examining whether these results apply to human lung cancers as well [as mice] and if so, how such information can improve treatment."
In a statement on the Cancer Research UK website, Dr Kat Arney, the charity's senior science information officer, said: "This is an interesting finding that may help to explain why some lung cancers spread aggressively through the body.
"It's too early to tell if this discovery will have an impact on the way that people with lung cancer are treated, but it certainly helps to advance our understanding of this disease."
Over 37,000 people are diagnosed with lung cancer each year.