Characteristic porphyrin-like autofluorescence in primary colon tumors and lymph nodes

摘要

Abstract: Fluorescence spectra of primary colon tumors, normal colonic tissue and lymph nodes were recorded ex vivo, following pulsed laser excitation at lambda equals 505 nm. Fluorescence was detected at zero delay and at a delay of 20 ns between the optical pulse and the opening of the intensified diode array detector. Generally, the spectra consist of a broad unspecific background (unspecific autofluorescence) and two characteristic fluorescence bands at lambda approximately equals 630 nm and lambda approximately equals 700 nm (specific autofluorescence). By delayed observation the intensity of the specific fluorescence diminishes less than the intensity of the unspecific background indicating a longer fluorescence decay time of the specific compared to the unspecific fluorescence. The fluorescence excitation and the fluorescence emission spectra of the specific autofluorescence as well as the fluorescence decay time are similar to those of porphyrins. Assuming that the relative amount of specific autofluorescence can be used to discriminate between primary tumors and normal colonic tissue or involved and non-involved lymph nodes, we have analyzed undelayed and delayed fluorescence spectra quantitatively to derive characteristic quantities for discrimination. We have investigated 18 primary colon tumors and associated normal colonic tissue as well as 174 lymph nodes. Out of 18 primary tumors classified by routine pathology we have correctly identified 16 by fluorescence analysis. Because of the rather weak specific autofluorescence in lymph nodes only 22 metastatically involved lymph nodes were detected out of 34 identified by routine pathology. Although the sensitivity of 65% is rather low a discrimination between involved and non-involved lymph nodes is of particular medical importance. !10