Spotting suspicious moles

At Frontiers in Optics 2010, scientists at Duke University in Durham, N.C., will present a new technique that aims to help doctors distinguish melanomas from harmless moles using high-resolution snapshots of suspicious spots.

To visually inspect the surface of the skin, doctors can use a hand-held lens and a bright light or microscopes and a technique called dermoscopy. But recent studies have found that diagnoses based on these images are often incorrect, because only the surface is visible, and the dangerous changes take place too deep to be seen. "There's quite a bit of variability in the diagnoses provided this way," said Thomas Matthews, a researcher at Duke. The best way to diagnose melanoma is still a biopsy -- the removal and analysis of a chunk of tissue from a growth -- but even then, experienced doctors often disagree on the diagnosis. This disagreement leads to false positives (which force unnecessary procedures and drive up healthcare costs) or false negatives (which can have fatal consequences).

Matthews and his colleagues at Duke's Center for Molecular and Biomolecular Imaging are adapting a laboratory imaging technique to provide new information about suspicious moles, both in vivo and in biopsy specimens. Skin contains two kinds of pigments, or melanins: pheomelanin, which is reddish or yellow, and eumelanin, which is dark and brownish. Some studies have suggested that a change in the ratio of these two pigments could signal that a harmless mole has turned malignant. Matthews' two-photon microscopy technique pumps a small amount of energy into the pigments (using much less power than a laser pointer), then watches the energy redistribute to give high-resolution images of their distributions in a spot of skin.

"No one has been able to look at where different melanins are organized in skin," said Matthews. "This opens up a whole new pathway of looking for melanoma." The most immediate application would be to reduce false positives and false negatives in interpreting biopsies; with further research, the scientists hope to better define how this information can be used to avoid biopsies altogether.

The presentation, "Nonlinear High-Resolution Imaging of Eumelanin and Pheomelanin Distributions in Normal Skin Tissue and Melanoma," takes place on Oct. 26 at the Frontiers in Optics (FiO) 2010/Laser Science XXVI -- the 94th annual meeting of the Optical Society (OSA), which is being held together with the annual meeting of the American Physical Society (APS) Division of Laser Science at the Rochester Riverside Convention Center in Rochester, N.Y., from Oct. 24-28.