Caractérisation de la transformation néoplasique de la peau par spectroscopies optiques sur fantôme de mélanome et carcinome épidermoïde murin photo-induit

Autofluorescence and diffuse reflectance spectroscopies were studied as non-invasive tools to discriminate different stages of skin neoplastic transformation and thus to help diagnose the two most lethal skin lesions: cutaneous melanoma and squamous cell carcinoma. Concerning melanoma, skin phantoms were made to simulate several melanoma thicknesses (Breslow index). Spatially-resolved diffuse reflectance spectroscopy (using five collection optical fibers set at five different distances from the excitation optical fiber) allowed discrimination (p<0.05) of melanoma layers, the thickness of which was 1 mm different. Since diffuse reflectance spectroscopy has already shown good results in assessing malignancy of pigmented skin lesions, such a spectroscopy could be used as a complementary tool of cutaneous melanoma diagnosis. Using ultra-violet induced squamous cell carcinoma of mouse skin, bimodal spectra (multi-excitation fluorescence and diffuse reflectance) were acquired throughout the 7 month-carcinogenesis. Histological sampling followed spectral acquisition and three histological classes were determined by histo-pathological examination: compensatory hyperplasia, atypical hyperplasia and dysplasia. A fourth "healthy" class consisted in the skin sampled on mice that were never irradiated (control group). Multivariate statistical analysis of the spectral data set showed that combining autofluorescence (best results obtained with a 410 nm excitation) and diffuse reflectance resulted in a 9% increase of specificity when discriminating the three types of hyperplasia from one another compared to each modality used alone. Such results need to be confirmed through clinical trials on human patients.L'objectif de ce travail de recherche est d'évaluer la capacité des spectroscopies optiques d'autofluorescence et de réflectance diffuse à caractériser les différents stades de la transformation néoplasique de la peau et ainsi d'aider au diagnostic des deux lésions de peau les plus létales : le mélanome malin et le carcinome épidermoïde. Dans l'étude portant sur le mélanome, un objet-test (« fantôme ») a été développé pour modéliser différentes épaisseurs de mélanome (indice de Breslow). La spectroscopie de réflectance diffuse résolue spatialement (grâce à l'utilisation de cinq fibres optiques réceptrices situées à cinq distances différentes de la fibre optique excitatrice) a montré sa capacité à discriminer (p