The studies by international scientists and Britain's Wellcome Trust Sanger Institute are the first comprehensive descriptions of tumour cell mutations and lay bare all the genetic changes behind melanoma skin cancer and lung cancer.

"What we are seeing today is going to transform the way that we see cancer," Mike Stratton of the Sanger Institute's cancer genome project told a briefing in London. "We have never seen cancer revealed in this form before."

The scientists sequenced all the DNA from both tumour tissue and normal tissue from a melanoma patient and a lung cancer patient using a technology called massively parallel sequencing. By comparing the cancer sequences with the healthy ones, they were able to pick up all the changes specific to cancer.

The lung tumour carried more than 23,000 mutations and the melanoma had more than 33,000.

Peter Campbell, also of the Sanger Institute, said the lung cancer study suggests a typical smoker develops one mutation for every 15 cigarettes smoked and the damage starts with the first puff. Lung cancer kills around 1 million people worldwide each year and 90 percent of cases are caused by smoking.

More info: http://www.reuters.com/article/idUSTRE5BF42O20091216