[Visualizing carcinomas of the mouth cavity by stimulating synthesis of fluorescent protoporphyrin IX]

The fluorescence diagnosis based on the aminolavulinic acid-stimulated porphyrin synthesis allows the detection of superficial tumors in a very early stage even when they are very small tumors. A fluorescence diagnosis of tumors in the oral cavity can be simply performed by rinsing with a 0.4% ALA solution for 20 min. This topical application avoids systemic side effects such as skin sensitization. The red fluorescent areas are visible to the naked eye; only a blue light source for fluorescence excitation is necessary and a suitable red filter for observation. In our study on 56 patients suffering from carcinoma of the oral cavity, 96% of the histologically confirmed carcinoma could be visualized via fluorescence. In 3 patients additional tumors were detected via fluorescence that were not visible otherwise. However, many patients show fluorescent areas with no correlation to the histological finding. It was verified that bacteria from the oral cavity also produce PpIX after ALA incubation, which leads to false-positive findings. Reduction of the false-positive findings was achieved by rinsing the oral cavity with hydrogen peroxide and by mechanical plaque reduction. This improves the reliability of a fluorescence-guided biopsy. However, suppression of the bacteria fluorescence is necessary for clinical use of this diagnostic method.