The cancerous method is a result of disturbed cell performance. This can be due to excess genetic and epigenetic changes inside the cell, expressed within the accumulation of body or molecular aberrations, that results in genetic instability. It's tough to assess the validity of individual factors which can cause a diseased condition; however, it can be suggested that interaction of various risk factors has the biggest contribution to cancer development and metastasis. Environmental and individual factors, together with genetic makeup contribute to the development of cancer. Medical research on malignant tumors has focused on the effects of environmental and genetic factors on cancer cases occurring and death rate. According to the information available, 80–90% of malignant tumors are a result of external environmental factors i.e. Carcinogens. Medical studies have indicated that the most factors leading to metastasis of cancer among humans are due to environmental factors which develop due to human activities. The studies show that smoking, excessive alcohol consumption and diet play an important role in metastasis of preexisting tumors. According to WHO, there might be ten million deaths by the end of 2020, out of which 7–8 million will be in developing countries and 2–3 million in developed countries. The aim of this study was to accumulate knowledge regarding the risk factors leading to metastasis of tumor and providing them with the most recent results.

Keywords : Cancer, Metastasis, Environmental factors, Biological Infection and metastasis, Physical factors, Chemical factors.