A tumour is a mass of abnormal cells formed by uncontrolled cell division (mitosis). Tumours form when the genes that regulate the cell cycle are mutated or wrongly expressed. There are two types.Benign tumours
• grow slowly, although they can become very large
• cells stay well differentiated (specialised) and have normal nuclei
• are surrounded by a capsule, so they stay compact and are easy to remove by surgery
• do not invade surrounding tissue or spread to other parts of the body
• rarely return after removal
• are usually harmless, but can cause damage by pressing on organs or blocking tubes, for example in the brain.Malignant tumours (cancers)
• grow rapidly
• cells become less specialised (poorly differentiated), with larger, darker nuclei
• have no capsule and grow projections into surrounding tissue (they are invasive)
• cells can break off and spread in the blood or lymph to form secondary tumours elsewhere; this is called metastasis
• often return after treatment
• usually need radiotherapy or chemotherapy as well as surgery, and are often life-threatening.
In short, the key differences are the speed of growth, whether the cells stay specialised, whether there is a capsule, and whether the tumour can spread. Cancer is dangerous mainly because of metastasis: secondary tumours damage vital organs and are hard to find and remove.
• grow slowly, although they can become very large
• cells stay well differentiated (specialised) and have normal nuclei
• are surrounded by a capsule, so they stay compact and are easy to remove by surgery
• do not invade surrounding tissue or spread to other parts of the body
• rarely return after removal
• are usually harmless, but can cause damage by pressing on organs or blocking tubes, for example in the brain.Malignant tumours (cancers)
• grow rapidly
• cells become less specialised (poorly differentiated), with larger, darker nuclei
• have no capsule and grow projections into surrounding tissue (they are invasive)
• cells can break off and spread in the blood or lymph to form secondary tumours elsewhere; this is called metastasis
• often return after treatment
• usually need radiotherapy or chemotherapy as well as surgery, and are often life-threatening.
In short, the key differences are the speed of growth, whether the cells stay specialised, whether there is a capsule, and whether the tumour can spread. Cancer is dangerous mainly because of metastasis: secondary tumours damage vital organs and are hard to find and remove.