A 'tumour paint' could help surgeons remove cancer more accurately and so help prevent the disease returning, US scientists say.
It can be difficult for surgeons to identify cancerous cells
In mice, the paint lit up cancer cells but not normal cells, so it could show surgeons exactly where tumours are.
This will help ensure they do not harm healthy tissues or leave cancerous cells behind during surgery, which could mean the tumours return.
The research is published in the journal Cancer Research.
But UK experts have warned more research is needed to find out exactly why the molecule only binds specifically to tumour cells, and to ensure it is not toxic in humans.
Researchers the Seattle Children's Hospital Research Institute and Fred Hutchinson Cancer Research Centre, developed the paint from a molecule called chemotoxin, which comes from scorpions.
Chemotoxin has previously been found to bind specifically to cancer cells in brain tumour biopsies, but not to normal brain cells, and in the new study they showed it bound specifically to a range of cancers.
The paint molecule emits light near the infra red spectrum, and this illumination helps surgeons identify cancerous cells.
Injecting the paint into mice, the researchers were able to light up brain tumours as small as 1mm in diameter without lighting up the surrounding normal brain tissue.
This would be helpful because surgeons currently have to rely on colour, texture and blood supply to tell which cells are cancerous, and these features can be subtle.
But removing tumours accurately is vital, and particularly important in the brain where surrounding neurons must not be damaged, and where about 80% of malignant cancers return at the edges of surgical sites.
Author Dr James Olsen said: "By allowing surgeons to see cancer that would be undetectable by other means, we can give our patients better outcomes.
"My greatest hope is that tumour paint will fundamentally improve cancer therapy."
The researchers hope the paint could be used to help remove many kinds of cancer.
They hope paint might be used in patients in as little as 18 months.
Professor John Griffiths, head of molecular imaging at Cancer Research UK's Cambridge Research Institute, said a way to improve brain surgery would be "extremely welcome".
He said: "The big problem with surgery for brain cancer is that tumours can infiltrate normal brain tissue, making it very hard to tell where the tumour ends and the normal tissue begins.
"If you could light up the tumour cells by shining an infrared beam on them, it might be very helpful."
But he said the researchers would need to demonstrate exactly why the paint bound specifically to cancer cells in mice, and prove that it also worked and was not toxic in humans.