An infrared imaging technique that can distinguish different types of skin cancer has been developed by scientists in France.

Olivier Piot at the University of Reims-Champagne-Ardenne led the team that developed the method, which uses a computer-based prediction algorithm to find and identify areas of different tumour types in skin tissue biopsies. The colour images produced are very simple to analyse, with each tumour type showing as a precise colour, with normal tissue shown in green. 

Piot explains that the current 'gold-standard' in non-melanoma skin cancer diagnosis uses histology - the microscopic analysis, by a pathologist, of the tissue morphology from stained sections of a biopsy. Piot's colour images are comparable to conventional stainings used in pathology labs, but are more informative since they are based on the tissue's biomolecular constituents such as DNA, RNA, sugars and proteins. Additionally, because the diagnostic tool is computer-based, the analysis is very rapid.

Infrared analysis (top) and staining (bottom) can be used to distinguish different areas of tumour tissue

The technique also avoids chemical dewaxing procedures required before many tissue analyses. Pathologists often embed tissue samples in paraffin to store them without the need for expensive cryogenic freezing. As it is not known whether removing the wax damages the tissue, much effort has been made to work directly on embedded tissues, something that Piot's technique is able to do. 'It opens the way to the analysis of embedded tissues for retrospective studies,' says group member Elodie Ly, adding that the method is also applicable to any type of tumour tissue, not just skin. 
 

This work comes after a series of studies performed by the same group with the aim at developing new methodologies in cancer diagnosis by infrared (IR) imaging. Cyril Petibois, an expert in optical diagnosis, at the University of Bordeaux, France, says that uses such as this are 'the heart of such analytical techniques.' He adds that, whilst the IR imaging requires long scanning times, it can compete with other molecular imaging methods where these lack sensitivity and/or spatial resolution. 'This is typically the case for small size or diffuse tumours, metastases, or even biopsy samples,' he says.

Ly explains that a future challenge remains in building a more robust database of spectral markers for particular tissue structures. It is essential to recognise different tissue appendages, such as follicles and glands in skin, and not to confuse them with the tumour. 'This is an important step before thinking about the potential application in clinics,' says Ly.

Kathleen Too

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