1. An apparatus for detecting and classifying tissue abnormality at a tissue site, comprising: (a) at least one source of electromagnetic radiation of selected wavelengths that excite different fluorescence intensity spectra in normal and abnormal tissue; (b) a receiver sensitive to the fluorescence intensity spectra; (c) a tissue site probe coupled to each source and to the receiver; and (d) an ensemble of neural networks, coupled to the receiver, for calculating from the fluorescence intensity spectra a probability that the tissue site is normal or abnormal, wherein each neural network in such ensemble comprises a radial basis function (RBF) network for generating an associated probability estimate and further including a means for combining the probability estimates into a single probability.