[Use of low-molecular fluorescent dyes for localizing tumor cells].

: A novel fluorescence microscopic technique, based on the application of low-molecular fluorescent dyes, was used to study the expression of the enzyme guanidinobenzoatase in malignant tumors of the head and neck area. Frozen sections have shown that moderately and highly differentiated squamous cell carcinomas express this enzyme, particularly in the area of tumor invasion. The protease is capable of breaking down fibronectin, an important component of the extracellular matrix. In less differentiated squamous cell carcinomas as well as malignant melanomas almost all tumor cells exhibited guanidinobenzoatase activity. The fluorescence microscopic technique presented here provides a fast and easy method for the localization of tumor cells. At the same time it provides a better understanding of the biological control of a tumor-associated protease, thus furnishing important new information on the invasion behavior of malignant tumors.