People develop cancer when the cell nucleus divides abnormally quickly and grows uncontrollably. The cancerous tumour presses on organs and body systems.

 

The cell nucleus is reprogrammed by other influences so that the cell divides excessively quickly, which leads to abnormal growth of an ulcer. The ulcer puts a strain on the surrounding organs and other systems. Some of these fast-growing cells can break off and be transported to other parts of the body.
Cancer is therefore a defect in the cell itself, which is usually triggered by external influences.
In many cases, the immune system recognises the error and repairs the cells. If the body is unable to correct the error and the cells grow uncontrollably into a tumour, this is known as cancer.

The larger the ulcer becomes, the more it presses on the surrounding tissue and draws nutrients from the body. The cancer cells need nutrients in order to grow. As the body is deprived of important nutrients, the person does not die from the cancer cells themselves, but from malnutrition.