Fluorescence diagnostics of skin tumors using 5-aminolevulinic acid and its methyl ester

Objective. The incidence of malignant skin tumors is rapidly increasing. Early diagnosis, determining the margins of the tumor, is extremely important to achieve good treatment results. We investigated fluorescence of protoporphyrin IX in skin carcinomas. The study aimed to compare the effectiveness of topical 5-aminolevulinic acid and methyl-aminolevulinate in determining the exact margins of skin tumors.
Materials and methods. Fluorescence measurements were performed in 126 patients with malignant, premalignant, and benign skin lesions for detection of the margins of squamous cell carcinoma and basal cell carcinoma. 5-Aminolevulinic acid or its methyl ester was applied to the skin lesion for 2–4 h, and the data of evaluated protoporphyrin IX fluorescence were correlated with the data of morphological tissue examination.
Results. Malignant tissue shows a specific red fluorescence when illuminated with blue-violet light, whereas no fluorescence was observed in normal skin. In 30% of cases, the delineation of neoplastic lesions excited by 5-aminolevulinic acid was slightly weaker than using methyl-aminolevulinate. A sensitivity of 95.4% and a specificity of 88.6% as well as positive and negative predictive values of 86.1% and 96.3%, respectively, were obtained.
Conclusions. Fluorescence diagnostics can be used for complete visualization of malignant skin lesions after topical application of 5-aminolevulinic acid or methyl aminolevulinate. It has been shown to be highly effective in the diagnostics of malignant superficial skin lesion. This method is applicable for detecting early superficial tumors, margins of tumors, and follow-up after therapy. Topical application of methyl aminolevulinate is slightly superior to 5-aminolevulinic acid in detection of lesion margins.