Photodiagnosis and Photodynamic Therapy of Cutaneous Melanoma

Abstract

Skin cancer is one of the most widespread tumours. However, despite the progress achieved in all clinical diagnostic techniques, the most severe of those tumours cutaneous melanoma, continues to be an important problem of social health. A large number of optical techniques have been recently applied in the clinical practice in view of obtaining qualitatively and quantitatively new data from cutaneous neoplasia. Due to their high sensitivity in detecting small changes, spectroscopic techniques are now widely used for detection of early changes in biological tissues. Fluorescence detection of normal and abnormal tissues is among the most promising such approaches as it makes use of naturally existing fluorescent molecules (in the case of autofluorescence) or added fluorescent markers (in the case of exogenous fluorescence) of high importance. Fluorescent markers are introduced wherever native fluorescence is not informative enough to be used for diagnostic goals due to the absence or non-specificity of the changes in the tumour vs. the normal tissues. The fluorescent diagnostic techniques are particularly suitable in diagnosing melaninpigmented cutaneous pathologies. Melanin is a pigment which absorbs strongly within practically entire visible spectral range. Its high content in these lesions leads to low penetration depth of the excitation light and a small amount of re-emitted fluorescent light that can be collected and used for fluorescent analysis of the pathology under investigation. Therefore, fluorescent diagnosis of melanin-pigmented neoplasia, such as cutaneous malignant melanoma and its differentiation vs. dysplastic precursors and similar benign skin pathologies, such as nevi, is an elaborate and challenging task for all researchers working in the field of biomedical photonics. Photodiagnosis (PD) and photodynamic therapy (PDT) have been established as emerging modalities for a variety of pathogenic conditions including pigmented melanoma (Awan et al., 2006; Davids and Kleemann, 2010). The number of cases of pigmented malignancies has been steadily increasing during the last decades in general, and, in particular, malignant melanoma (MM) incidence has also increased. Melanomas are the most aggressively developing form of dermatological cancers due to the difficulty of diagnosis at an early stage combined with the low rate of success of