Among the causes of malignant tumors, it is possible to separate the influence of environmental factors: chemical, physical, biological agents and the effect of internal environment of the body. Considerable importance are indirect signs: "lifestyle", a genetic predisposition, lesions and diseases of different organs and organ systems.
Of chemical agents in the first place are polycyclic aromatic hydrocarbons (PAHs) -- benzopyrene, benzidine, 2-naphthylamine, 2-acetylaminofluorene. Are substances that cause tumors predominantly on the application (contact); substances distant action is not on the injection, and selective damage of the organs, and substances multiple actions, which cause tumors in different organs and tissues.
Carcinogens (agents that cause permanent changes in physical or chemical properties) can be metals such as arsenic, chromium, Nickel, cobalt, lead, zinc, asbestos, a number of polymeric materials: nylon, Teflon, cellophane, nylon, plastic.
Physical agents -- the effect of ionizing radiation (x-rays, gamma rays, protons, alpha - and beta-particles) ultraviolet rays, mechanical trauma to tissues
Biological agents -- effect of oncoviruses to the development of malignant tumors. Oncovirus are divided into DNA - and RNA-containing.
RNA-containing retroviruses that -- and oncornavirus. Often they are striking animals, birds, reptiles and mammals. DNA-containing viruses is an adenovirus, the herpes viruses, the virus group smallpox, papiloma viruses.
Although many of the tumors arise due to the action of external chemical or other agents that cause the development of a number of neoplasms are specific conditions of the internal environment associated with genetic, hormonal and metabolic disorders, is of great importance and age and "lifestyle" -- Smoking and alcohol, various diseases such as diabetes mellitus, atherosclerosis, hypokinesia (limited physical activity), immune status, stress, various skin lesions, mucous membranes and the subsequent appearance of cancer.