Cancer — Types, Features and the p53 Guardian

Cancer is a disease of uncontrolled cell division, and cancers are classified by the type of tissue they arise from. Carcinomas arise from epithelial tissue (such as skin or the lining of internal organs) and are the most common type; sarcomas arise from connective or supportive tissues such as bone, cartilage or muscle; leukemias arise from blood-forming tissue, causing the excessive production of abnormal white blood cells; and lymphomas arise from lymphoid tissue and lymph nodes. Some cancers are described as familial, meaning they show a hereditary predisposition and tend to run in families because of inherited gene mutations, in contrast to cancers that arise mainly from other, non-inherited causes.

Cancer cells show several characteristic features that set them apart from normal cells: they divide continuously and without control, ignoring the normal signals that would otherwise regulate cell division; they lose contact inhibition — normal cells stop dividing once they touch neighbouring cells, but cancer cells do not, and instead pile up into a growing tumour mass; they can invade and destroy neighbouring normal tissue; and they can metastasize, breaking away from the original tumour and spreading through the blood or lymph to establish new tumours at distant sites in the body. …