Induced fluorescence of serotonin in paraffin sections from carcinoid tumors

The detection of argentaffin cells and carcinoid tumor cells would be greatly facilitated if it were possible to apply methods of induced fluorescence directly on paraffin sections. We have subjected 5 microgram thick sections from paraffin blocks containing carcinoids to different procedures for induced fluorescence. These include formaldehyde vapor at 80 degrees C for 1 hour, 5% paraformaldehyde solution at room temperature followed by heating to 80 degrees C for 15 min, and sucrose-phosphate buffer-glyoxylic acid solution either for 3 seconds at room temperature followed by heating to 80 degrees C for 15 min or 15 min at 60 degrees C in the solution. The different procedures were applied to sections which were non-deparaffinized, deparaffinized or deparaffinized and rehydrated to various degrees. With all procedures used we were able to induce histofluorescence of argentaffin cells and carcinoid tumor cells, and it was confirmed by microspectrofluorometry that the fluorophore originated from serotonin. Best results, when morphology was taken into consideration, were obtained with sections deparaffinized, transferred to 96% ethanol and then exposed to formaldehyde vapor.