ABSTRACT
Cancer is a disease of “chaos,” a breakdown of existing biological order and rules of tissue homeostasis. In the human body, normal healthy organs obey a tightly regulated homeostatic mechanism that has evolved through millions of years of refinement. This fine balance between cellular growth and apoptosis (programmed cell death) is the key to normal tissue homeostasis. The different types of cancer have been classified based on their clinical behavior and origin in different cell types. Histopathology is the conventional and the most reliable method of classifying tumors, by visualizing them under a microscope. Microscopic examination of thin tumor sections prepared from patients’ tumor tissues serves as a powerful tool to both characterize and categorize tumors. The incidence of different types of cancer varies between populations deriving from different ethnic and cultural backgrounds. Epidemiological studies have revealed that rates of cancer death and risk of onset of cancer in different organs vary with geographical location in which the victims reside.
