Cancer 'can appear out of nowhere'

Most of the time cancer seems to creep up gradually as cells become increasingly abnormal.

But sometimes cancer appears out of nowhere. According to the new research, the cause is likely to be a phenomenon called chromothripsis, or "chromosome shattering".

The effect is to tear chromosomes apart, after which their components are reassembled in a patchwork fashion.

Genetic mistakes often result that are serious enough to lead to cancer.

"It seems that in a single cell in a single event, one or more chromosomes basically explode - literally into hundreds of fragments," said study leader Dr Peter Campbell, from the Wellcome Trust Sanger Institute in Hinxton, Cambridgeshire. "In some instances – the cancer cases – our DNA repair machinery tries to stick the chromosomes back together but gets it disastrously wrong. Out of the hundreds of mutations that result, several promote the development of cancer."

The findings are published today in the journal Cell.

Dr Campbell's team made the discovery after examining cancer samples using advanced DNA sequencing technology.

Why the chromosomal explosions occur remains a mystery. Dr Campbell suspects single pulses of ionising radiation may play a role.

Radiation, which can be natural or from manmade sources such as X-rays, is known to cause DNA breaks that cut through chromosomes.

Another possible cause may be attrition of telomeres, structures that "cap" strands of DNA and keep them stable.