A newly-discovered part of our immune system could be harnessed to treat all cancers, say scientists.
The Cardiff University team discovered a method of killing prostate, breast, lung and other cancers in lab tests.
The findings, published in Nature Immunology, have not been tested in patients, but the researchers say they have "enormous potential".
Experts said that although the work was still at an early stage, it was very exciting.
What have they found?
Our immune system is our body's natural defence against infection, but it also attacks cancerous cells.
The scientists were looking for "unconventional" and previously undiscovered ways the immune system naturally attacks tumours.
What they found was a T-cell inside people's blood. This is an immune cell that can scan the body to assess whether there is a threat that needs to be eliminated.
The difference is this one could attack a wide range of cancers.
"There's a chance here to treat every patient," researcher Prof Andrew Sewell told the BBC.
He added: "Previously nobody believed this could be possible.