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Cancerous Human Lung
This dissection of human lung tissue shows light-colored cancerous tissue in the center of the photograph. At bottom center lies the heart. While normal lung tissue is light pink in color, the tissue surrounding the cancer is black and airless, the result of a tarlike residue left by cigarette smoke. Most lung cancer begins in the cells lining the main air passages, or bronchi. In their cancerous state, these cells lack the cilia that normally catch and eliminate foreign particles inhaled into the lung. Mucous ordinarily cleared by bronchial cilia becomes trapped, blocking air passages. Lung cancer accounts for the largest percentage of cancer deaths in the United States, and cigarette smoking is directly responsible for the majority of these cases..