Laser Applications and Autofluorescence

Abstract

The diagnostic pathway for oral suspicious lesions usually starts with the clinical examination based on inspection and palpation of the oral mucosa. Such a phase is strongly related to the experience of the operator. Moreover, oral epithelial dysplasia and early oral carcinomas may already be present within areas of macroscopically intact oral mucosa. A great interest for techniques potentially improving the diagnostic accuracy has developed in several fields of surgical oncology in order to increase the specificity and sensitivity of the conventional diagnostic pathway. The development of noninvasive methods for real-time screening of neoplastic changes in oral cavity may be associated with the improvement of patients’ quality of life and survival rate. The analysis of tissue autofluorescence (AF) for improving sensitivity and specificity in cancer diagnosis has been proposed for different organs, including colon, lung, cervix, and esophagus. Particularly, there are several evidences supporting the effectiveness of this technique in head and neck cancer diagnosis. Autofluorescence shows high specificity and sensitivity for oral cancer and precancerous lesions: 72.4% and 63.79%, respectively. It can also provide valuable information for diagnosis, for planning of margin resection in surgical excision, and for monitoring the therapeutic response during follow-up. Direct visual fluorescence examination (DVFE) is based on the action of irradiation of specific wavelengths, between 375 and 440 nm, which excites some natural fluorochromes which show fluorescence in the range of the green color. The analysis of the lesions with AF tools must be performed in a dark environment to avoid the interference of white light wavelengths and to improve the quality of recorded images. Healthy oral mucosa emits fluorescence, detectable as green light. Cell and tissues within dysplastic and malignant lesions display modifications of the amount, distribution, and chemical–physical properties of the endogenous fluorophores. This results in an autofluorescence pattern variation that can be potentially used at diagnostic level. Loss of autofluorescence (LAF) seems to increase in correspondence to the progression of dysplasia, and altered tissue appears dark (brown to black). LAF in dysplasia and carcinoma seems to be connected to different mechanisms, such as altered metabolic activity of dysplastic keratinocytes, altered structure of subepithelial collagen, and absorbance of light by increased blood circulation due to inflammatory phenomena in dysplastic tissue and cancer. AF can be used for guiding incisional biopsy and in the excision to identify the resection margins.