a method and apparatus for detecting the presence of cancerous tissue using native visible luminescence . the tissue to be examined is excited with a beam of monochromatic light that causes the tissue to fluoresce over a spectrum of wavelengths . the intensity at which the excited tissue fluoresces can be measured either over a spectrum or at a predetermined number of preselected wavelengths . by determining the wavelength at which maximum intensity are attained for the tissue in question and by comparing these peak wavelengths , either visually or electronically , to the peak wavelength derived from a known non - cancerous tissue , or by comparing the luminescence spectrum of the excited tissue with the luminescence spectrum of a known noncancerous tissue and / or known cancerous tissue or the excitation spectra of the excited tissue with the excitation spectra of known cancerous and / or known non - cancerous tissue one can determine the carcinomatoid status of the tissue in question . once it has been determined that the tissue is cancerous , it may by destroyed by ablation by exposing it to a beam of light from a high power laser . the invention is based on the discovery that the visible luminescence spectra for cancerous and non - cancerous tissue are substantially different and that the differences are such that visible luminescence from tissue can be used to detect the presence of cancer and also on the discovery spectral profiles of excitation spectra are similarly different .