Paris (AFP) - The black spots on old banana peels may unlock a faster, easier diagnosis of human skin cancer, boosting survival chances, scientists said Monday.

When bananas ripen, their skin is covered in small, round black spots caused by an enzyme known as tyrosinase.

The same enzyme is present in human skin, and in greater quantities in people suffering from melanoma -- a potentially deadly form of skin cancer.

A team of scientists used this observed commonality to build a cancer scanner, which they then refined and tested at length on banana peels before moving on to human tissue.

First, researchers at the Laboratory of Physical and Analytical Electrochemistry in Switzerland concluded that the enzyme is a reliable marker of melanoma growth.

In the earliest stage 1 of cancer, the enzyme is not very apparent, becoming widespread and evenly distributed in stage 2, and unevenly distributed in stage 3 -- by when the cancer has started spreading to other parts of the body.

The earlier the cancer is detected, the greater the chances of survival.

According to the American Cancer Society, people have a 10-year survival rate of 95 percent if the melanoma is detected in stage 1 -- falling to 43 percent by mid-stage 3.

The team developed a scanner and tested it on banana peel spots -- which are roughly the same size as melanoma spots on human skin.

"By working with fruit, we were able to develop and test a diagnostic method before trying it on human biopsies," team leader Hubert Girault said in a statement.

The scanner has eight flexible microelectrodes, spaced like comb teeth, that pass over the skin to measure the quantity and distribution of tyrosinase.

"This system could obviate the need for invasive tests like biopsies," the team said.

Girault believes the scanner could be used one day to destroy tumours, hopefully rendering biopsies and even chemotherapy unnecessary.

"Our initial laboratory tests showed us that our device could be used to destroy the cells," he said.

The research was published in the German science journal Angewandte Chemie.