A cancerous cell is characterized by morphological and metabolic changes which are the key features of carcinogenesis. Adenosine triphosphate (ATP) in cancer cells is primarily produced by aerobic glycolysis rather than oxidative phosphorylation. In normal cellular metabolism, nicotinamide adenine dinucleotide (NADH) is considered as a principle electron donor and flavin adenine dinucleotide (FAD) as an electron acceptor. During metabolism in a cancerous cell, a net increase in NADH is found as the pathway switched from oxidative phosphorylation to aerobic glycolysis. Often during initiation and progression of cancer, the developmental regulation of extracellular matrix (ECM) is restricted and becomes disorganized. Tumor cell behavior is regulated by the ECM in the tumor micro environment. Collagen, which forms the scaffold of tumor micro-environment also influences its behavior. Advanced optical microscopy techniques are useful for determining the metabolic characteristics of cancerous, normal cells and tissues. They can be used to identify the collagen microstructure and the function of NADH, FAD, and lipids in living system. In this review article, various optical microscopy techniques applied for breast cancer research are discussed including fluorescence, confocal, second harmonic generation (SHG), coherent anti-Stokes Raman scattering (CARS), and fluorescence lifetime imaging (FLIM).
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