Abstract: In in vitro illumination of HE stained frozen sections of healthy lymph nodes with different excitation wavelengths (365-546 nm) results, at least, in three different fluorescence emission peaks located at ca. 460, 545 and 592 nm. These might correspond to NADH, flavins, and protoporphyrin. Lymph nodes invaded by cancer cells resulted in the same spectra; they differ, however, in intensity. The HE stained cryosections can also be used for determining the spatial distribution of the endogenous fluorophores. In accordance with results obtained previously, cancer tissue of lymph nodes exhibit a small fluorescence intensity only. The adjacent healthy tissue shows a rather high intensity in comparison to normal values. Furthermore, necrotic tumor cells at different stages including its final degradation products (minute debris) can be detected by using a double illumination technique. HE stained frozen sections were illuminated concomitantly with a halogen lamp (bright-field transmitted light technique) and an Hg high-pressure lamp with an appropriate filter (395-440 nm) (incident light fluorescence technique). The minute debris can be seen in an area in which the histological image shows hardly anything. The fluorescence intensity observed in healthy tissue adjacent to the tumor, seems to decrease with progression of necrosis. Thus, autofluorescence studies on lymph nodes seem to be able to detect metastasis and the different stages of necrosis more clearly than the methods used conventionally. !1
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