The salient properties of laser light and the way light interacts with biological tissues and molecular constituents of tissues offer possibilities for detection and diagnosis of cancer. In particular, the wavelength selectivity of tunable lasers, narrow bandwidth around the selected wavelength, and spectral brightness enable probing of key molecular constituents of tissues, and endow laser-based techniques with much desired diagnostic potential. This article presents an overview of some recent developments in optical imaging and optical biopsy of different types of cancers, and illustrates the diagnostic role of the color of light.

Key words: Optical imaging; Optical biopsy; Laser; Cancer; Breast cancer; Prostate cancer; Tissue optical properties; Absorption spectra; Emission spectra; and Stokes excitation spectroscopy.