Cancer is a multifunctional disease in the sense that it may, but does not necessarily, arise through the influence of several or all of the following four factors: environment, genetic predisposition, available healthcare system and lifestyle.

Known risk factors are:

• Lifestyle and diet: high-fat diet, tobacco and alcohol consumption
• Genetic causes, hereditary risk factors (genetic predisposition)
• Benign proliferation of glandular and connective tissue (proliferative mastopathy)
• Viral infections
• Disturbances of the immune system