Radiation Oncology
Cancer is characterized by uncontrolled growth, and the ability to infiltrate surrounding tissues and spread to distant sites. The clinical manifestations of malignancy depend in part on the innate potential of the growth, but also on host factors, anatomical, metabolic and immunological, which may encourage or inhibit the neoplastic process. The resulting spectrum of malignancy extends from tumours which may stay unchanged for several years, very rarely metasta size and which may have no impact on life expectancy, to tumours which may kill within days of the first indication of their presence.
Most cancers arise from a mutation in a single cell and therefore represent a monoclonal population, but some growths are polyclonal, indicating that they have developed following more than one mutation.