With just a drop of blood doctors may one day be able to detect pancreatic cancer in its early stages, before it has become deadly, a new study suggests.

An international team of researchers was able to identify 100 percent of patients with late-stage pancreatic cancer, as well as those with earlier stage disease, by looking for a protein in the blood that is made in abundance by tumor cells.

That protein turns up in tiny virus-sized particles, called exosomes, which are excreted by all of the body’s cells, according to the study published in Nature. But, by good fortune, the protein turns up in exosomes only when there is cancer, so its presence could be an early, and testable, marker for the disease.