Lasers Detect Melanoma Better than Doctors

 For the first time, scientists have been able to tell the difference between cancerous and non-cancerous tissues by looking at the chemicals they contain. Duke University researchers used lasers to probe suspicious moles and diagnose malignant melanomas.

Melonoma is not only the worldwide cause of most deaths related to skin-cancer, the most common cancer in the United States, but it's also notoriously hard to diagnose correctly. Given the amount of diagnoses, even it's 85 percent accuracy rate translates to hundreds of thousands of misdiagnoses a year and the equivalent amount of medical procedures -- typically meaning biopsies.

In the trial published on February 23rd in Science Translational Medicine, the Duke researchers correctly identified all 11 melanoma cases in a group of 42 skin samples.

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The technique used two low-energy lasers that together probe tissue samples on a slide (the team is working on a version that will work without slides, but that may be a few years coming). Both lasers pump narrow -- smaller than a laser pointer -- beams into the samples. By watching how the energy redistributes inside the tissue, the researchers can find the exact microscopic location of various pigments. One pigment in particular, eumelanin, is generally found in much higher concentrations in a melanoma than in healthy tissue. So, the team used eumelanin as their diagnostic meter.

This is better than what the Duke news story refers to as “a 17th century technique,” whereby a doctor examines tissue on a slide with a regular light microscope. Another diagnostic alternative is sending tissue samples to a pathology lab; if doctors are still unsure though, this might lead to additional biopsies for the patient.

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Although adding such lasers to standard microscopes costs about $100,000 -- and an eventual tool to examine moles pre-removal would likely cost more -- the eventual healthcare savings from reduced number of biopsies could still make it worthwhile. For now though, the lasers can already be used post-removal for diagnosis, at least improving accuracy about the need for further biopsies.

In their next step, the team is developing the tool so that it can detect skin cancer on mice without removing any tissue.

Image: Science AAAS