Excitation-emission matrices measurements of human cutaneous lesions: tool for fluorescence origin

Abstract

The light induced fluorescence (LIF) technique has the potential of providing real-time diagnosis of malignant and premalignant skin tissue; however, human skin is a multilayered and inhomogeneous organ with different optical properties that complicate the analysis of cutaneous fluorescence spectra. In spite of the difficulties related to the detection and analysis of fluorescent data from skin lesions, this technique is among the most widely applied techniques in laboratorial and pre-clinical investigations for early skin neoplasia diagnosis. The important point is to evaluate all sources of intrinsic fluorescence and find any significant alterations distinguishing the normal skin from a cancerous state of the tissue; this would make the autofluorescence signal obtained useful for the development of a non-invasive diagnostic tool for the dermatological practice. Our investigations presented here were based on ex vivo point-by-point measurements of excitation-emission matrices (EEM) from excised tumor lesions and the surrounding skin taken during the daily clinical practice of Queen Jiovanna- ISUL University Hospital, Sofia, the local Ethical Committee’s approval having already been obtained. The fluorescence emission was measured between 300 nm and 800 nm using excitation in the 280–440 nm spectral range. In the process of excitation-emission matrices (EEM) measurements we could establish the origin of the autofluorescence and the compounds related by assigning the excitation and emission maxima obtained during the experiments. The EEM were compared for normal human skin, basal cell carcinoma, squamous cell carcinoma, benign nevi and malignant melanoma lesions to obtain information for the most common skin malignancies and their precursors. The main spectral features and the applicability of the technique of autofluorescent spectroscopy of human skin in general as an initial diagnostic tool are discussed as well.