Cancer – very few other diseases stir up such strong emotions in those affected and their relatives as this diagnosis. But how does cancer actually develop? What causes it? And how do benign tumours differ from malignant ones?

Cancer is a collective term which encompasses around 150 different malignant organ tumours and diseases of the lymphohaematopoietic system. After cardiovascular disease, it is the second most common cause of death in Switzerland. However, a cancer diagnosis is not a death sentence as around half of the more than 30,000 new cases every year can be cured.

As long as a cancer remains localised, the treatment success rates are much better than if metastases have already formed. For this reason, early detection and timely treatment are crucial.


Cancer develops when normal cells change – often during various intermediate steps – into malignant cells that start to divide uncontrollably. When the body’s defence mechanism is not able to destroy them, more and more diseased cells are created to form a localised growth (tumour). The surrounding tissue is subsequently also affected (infiltration). Cancer cells can travel via the lymphatic and circulatory systems to reach other parts of the body, where they then create new cancer growths (metastases). In the case of leukaemia and certain lymphatic cancers, the cancer cells distribute themselves rapidly throughout the entire body.

Benign tumour

Cancer, in other words the unrestricted growth of malignant tumours, is the result of mutations in the genetic material inside cells. These mutations can be caused by a variety of different factors, including genetically inherited risk factors, the natural ageing process, as well as external influences like lifestyle, harmful substances or infections. Some of these risk factors can be avoided – others can’t. Around a third of all cancers are caused by preventable causes such a smoking, alcohol consumption or an unbalanced diet.

Malignant tumour

Malignant tumours are cell growths with altered genetic material. These cells are no longer controlled by the body, so they are characterised by unrestricted growth. As they grow, they infiltrate healthy tissue and destroy it. The cells of a malignant tumour can travel through the bloodstream to reach other parts of the body. There they can form metastases, which can destroy the surrounding tissue.