Surgeons may soon have a new tool to help locate early-stage cancerous growths; a spray that turns fluorescent green when it comes into contact with tumors.

The spray is clear, but contains a non-toxic dye that almost immediately glows bright green when it reacts with enzymes produced by cancerous tumors.

The fluorescent spray was developed by Hisataka Kobayashi, a researcher at the U.S. National Cancer Institute near Washington D.C.

The problem with many cancers, according to Kobayashi, is that their early-stage tumors are too small to be seen with the naked eye.

"The tiny, tiny cancer is very hard to see and then very hard to handle," says Kobayashi, "and very hard to see whether it's removed from the body or not."

Current attempts to image tumors - if they are even detectable - can take hours to days.

Kobayashi and colleagues conducted experiments with mice in which human ovarian tumors had been induced. Within a minute of spraying the cancerous tissue inside the animals' open abdominal cavities, researchers easily spotted the small tumors, which glowed bright green.

Kobayashi says the spray can help surgeons detect even the tiniest tumors which normally would be missed, increasing the chances for successful cancer surgery and making a recurrence of the cancer less likely.

Kobayashi says he expects the spray to be approved for human use by U.S. regulators within two to three years. His study describing the fluorescent cancer spray is published in the journal Science Translational Medicine.