The common painkiller aspirin could be used to treat certain types of cancer, according to scientists.
They believe it can fight a rare form of skin cancer and some breast cancers.
The scientists say the drug can help to reduce inflammation in the body, which causes some of these cancers.
The study, published in the journal Nature, adds to growing evidence that the humble painkiller can be used to fight a wide range of diseases.
Previous studies have suggested aspirin, which is more than 100 years old, could help to treat conditions like heart disease and strokes.
In this latest study, scientists from the Institute of Cancer Research in London examined a rare form of cancer called turban tumour syndrome or cylindromatosis.
This type of cancer causes huge mushroom shaped tumours to grow out of the scalp and other hairy parts of the body.
While the tumours are benign, they can cause horrendous disfigurement and discomfort and may eventually turn into life-threatening cancers.
The syndrome is genetic. People with a damaged version of a gene called CYLD are most at risk of developing it.
Professor Alan Ashworth and colleagues at the institute found that a fault in this gene means the body does not respond normally to diseases or tissue damage.
In particular, the body is unable to reduce inflammation that may occur as a result of disease or tissue damage.
In fact, the body tends to over-react, which can lead to the large, swollen tumours characteristic of turban tumour syndrome.
This occurs because the body is unable to keep a key molecule, called NF-kappaB, in check. This molecule becomes overactive in a number of different types of cancer, including some breast cancers.
There is evidence to suggest too much of it can fuel the growth of cancer cells and keep them alive much longer than they should.
The scientists believe anti-inflammatory drugs like aspirin could offer a solution to this problem, by countering the effects of this molecule.
They are now planning to test their theory on patients with turban tumour syndrome.
"It's important that we put the theory to test in patients as soon as we can," said Professor Ashworth.
"In the case of turban tumour syndrome, we think anti-inflammatory drugs could be rubbed into tumours in gel form in order to shrink them or perhaps given to younger patients before they have begun to show signs of the disease, as a preventive measure."
But he said aspirin could also help people with other cancers.
"We know inflammation can play a role in the development of a number of other cancers too, so it could be that aspirin will find a range of uses as a cancer treatment.
"First though, we need much more information about the detailed effects of the inflammatory response in these patients."
Professor Robert Souhami, director of clinical research at Cancer Research UK which funded the study, welcomed the findings.
"Even after a hundred years, we're still uncovering new possibilities for the use of aspirin," he said.
"It's another example of the way in which basic research opens up possibilities for treatment, in this case with a cheap and readily available drug."