The mass of extra cells forms a growth or tumour. Tumours can be benign or malignant. Benign tumours are not cancerous. They often can be removed and, in most cases, they do not come back. Cells in benign tumours do not spread to other parts of the body, and they are not life threatening.
Malignant tumours are cancerous.
Cells in malignant tumours are abnormal and divide without control or order. These cancer cells can invade and destroy the tissue around them. Cancer cells also can break away from a malignant tumour and enter the bloodstream or lymphatic system vessels. This process, called metastasis, is how cancer spreads from the original tumour to form new tumours in other parts of the body. Other CanWest Global Communications Corp. Sites Our privacy policy .