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Definition

Cancer – a complex disease

Cancer is not a single disease - more than 250 different types of this complex illness have been identified so far. One thing all cancers have in common is the malignant (harmful) uncontrolled growth of cells in an organ or tissue.

Most healthy cells in our bodies go through a cycle of growth and division. Occasionally, cell division results in damage to genetic material. The body can usually repair damaged cells, but in cancer, cell growth continues unchecked. Normally our immune system combats new cancer cells but if they are not recognised they can slip through the net.

Cancerous cells that escape detection can divide again and again to form a lump of cancer cells known as a tumour. As tumours grow they can displace or destroy surrounding tissue. Cells can also break off the tumour and be carried around the body in the blood or lymphatic system. This can lead to the formation of secondary tumours, known as metastases, in distant organs or tissues. In cancers of the blood, the cancer cells can circulate in the blood and can stop the normal production of blood by the bone marrow.

How quickly a tumour grows depends on the speed at which the cells divide. Some divide very rapidly, others slowly. The blood supply of a tumour influences growth rates since blood transports nutrients and oxygen to the tumour cells. Some tumours can even cause new blood vessels to grow into the tumour from adjacent areas, giving them a richer supply of nutrients and oxygen and enabling them to grow faster.

Understanding of the molecular mechanisms of cancer development and how cancers spread has continually improved. For Roche, this knowledge helps our scientists to target the processes that lead to cancer.