Malignant neoplasms are different types of cancer. Cancer is not one disease but a group of over 100 diseases that have in common the uncontrolled multiplication of abnormal cells. The human body is made up of billions of cells of many types. In a particular cancer there will be a particular type of abnormal cell. Usually cancers start with a localized tumour or swelling consisting of abnormal cells, which increases in size and spreads. Further tumours can appear away from the original site; these are called metastases. Most untreated cancers cause death within months or a few years of diagnosis. Treatment is sometimes completely successful (when there are no live cancers cells remaining), sometimes prolongs life by a number of years, sometimes just eases particular symptoms (which may be its purpose), or sometimes turns out to be ineffective in a particular case. There is often a much better chance of successful treatment if treatment is started when a cancer is still small and before it has spread anywhere (no metastases).
Malignant neoplasms (cancers) caused 12% of all deaths worldwide in 2002, an average of 1144 deaths per million people per year.