Cancer arises from abnormal changes of cells that divide without control and are able to spread to the rest of the body. These changes are the result of the interaction between the individual genetic factors and three categories of external factors: a chemical carcinogens, radiation, hormonal imbalance, genetic mutations and genetic factors. Genetic deviation leads to the initiation of the cancer process, while the carcinogen may be a key component in the development and progression of cancer in the future. Although the factors that make someone belong to a group with a higher risk of cancer, the majority of cancers actually occur in people who do not have known factors. The aim of this descriptive mini-review, generally, is to shed light on the main cause of cancer and vital factors in cellular system and extracellular system that may be involved with different types of tumors.
 

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