A method of examining a two-dimensional tissue sample comprising the steps of:
- a) exciting the two-dimensional tissue sample with light at a first wavelength, whereby native fluorescence is emitted therefrom;
- b) measuring the intensity of the native fluorescence emitted from the two-dimensional region at a second wavelength as a function of location within the two-dimensional tissue sample;
- c) exciting the two-dimensional tissue sample with light at a third wavelength, whereby native fluorescence is emitted therefrom;
- d) measuring the intensity of the native fluorescence emitted from the two-dimensional tissue sample at said second wavelength as a function of location within the two-dimensional tissue sample;
- e) said first and said third wavelengths being such that the difference of intensities of the resultant native fluorescence measured at said second wavelength is indicative of the carcinomatous condition of the tissue sample;
- f) determining the difference of intensities measured at said second wavelength to obtain a value for each location within the two-dimensional tissue sample;
- and
- g) generating a map using said values.