A team of British scientists has identified a genetic mutation that may trigger up to 70 percent of cases of the most deadly form of skin cancer - melanoma.
Previous studies have shown that the BRAF gene was often damaged or mutated in melanomas - but it is not known whether this was a cause or result of the cancer.
The Institute of Cancer Research study shows that acquiring the mutation can be the first in a cascade of genetic changes leading to melanoma.
It confirms that BRAF is a driving force behind the disease and could be the trigger that causes melanoma.
"We know that excessive sun exposure is the main cause of skin cancer, but not much is known about the genetics behind it," the BBC quoted lead author Professor Richard Marais, as saying.
"Our study shows that the genetic damage of BRAF is the first step in skin cancer development. Understanding this process will help us develop more effective treatments for the disease," Marais added.
Over-exposure to sunlight causes at least two thirds of all malignant melanomas. This excessive exposure damages DNA and causes genetic mutations.
The study features in the journal Cancer Cell.