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A tumor (neoplasm) is a severe cellular reaction, which defies this regulation so that abnormal growths of cells replace or distort normal tissues or organs. Tumors may be benign or malignant. Benign tumors do not invade surrounding tissue or grow in other places of the body (metastasize) whereas malignant tumors (cancers) have that capability. There are many types of cancer and they can occur in virtually any tissue or organ. Cancer develops gradually over a long period of time. Lifestyle factors (e.g., smoking and alcohol) are considered the cause of most cancer cases. Carcinogenesis is a
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