A test that measures how stretchy cells are could revolutionise the way doctors spot whether cancers have spread, say German researchers.
Cancer cells can be seen under a microscope
The laptop-sized gadget can give a diagnosis using as few as 50 cells and avoids the need to cut out tissue.
The University of Leipzig inventors, who spoke at a UK conference in Warwick on Tuesday, said it was 1,000 times more accurate than traditional tests.
The same technology could also be used to find stem cells in blood, they said.
But cancer experts stressed that the technology was still in its infancy and that it would not replace conventional cancer tests yet.
It works by using a special laser beam of unfocused light to stretch and measure individual cells one by one without killing them.
Cancer cells tend to be more elastic than healthy cells.
Just 50 tumour cells need to be present in a sample for the optical stretcher to be able to diagnose cancer.
In comparison, more traditional methods, such as looking at tissue samples under a microscopy, need up to 100,000 tumour cells to be present to make a diagnosis.
Its big advantage is that it should be able to identify cancers that are about to spread, according to the researchers.
Usually, doctors check whether a cancer has spread by looking for distant tumours in other parts of the body away from the original tumour site.
But sometimes it is not possible or is dangerous to cut out tissue samples from these secondary sites to check for cancer spread.
With the new technology, small samples of cells could be removed from sites around the body using fine needles and then analysed, said the German scientists.
Lead researcher Professor Josef Kas said: "Of all the physical properties of a cell, elasticity is the one which varies most dramatically between normal and cancer cells."
He told the Institute of Physics meeting, Physics 2005, how this made stretching the most sensitive method known for identifying cancer.
Cancer Research UK's Professor Peter Sasieni said: "It has been observed before that cancer cells have a less well defined skeleton than normal cells and so it is reasonable that they would change shape more in response to external forces.
"Nevertheless, it is rather premature to be talking about a machine that could replace a microscope for cancer screening or the study of lymph nodes to assess tumour spread.
"This machine is highly innovative and it is hoped that the team in Leipzig will collaborate with others to determine the clinical relevance of their invention."
Professor Kas said the optical stretcher could also be used to separate out stem cells from adult blood, again, based on their elasticity.
Stem cells are immature cells that have the ability to become any kind of tissue in the body.
Scientists can harvest them from embryos, but this has raised ethical concerns.
The optic stretcher might help get round this, said Professor Kas.