Introduction

Abstract

Information about cancer is increasing very rapidly. There are several reasons for this. First, because cancer is not one, but over 200 separate diseases, each with its own causes, natural history, and selection of treatments, each of these cancers is now studied individually. Second, since in many countries, but not all, many infectious diseases which used to be the major causes of death for large fractions of populations are now better controlled, cancer has become a more common problem and accordingly has been receiving more scientific attention. Finally, discoveries in the basic sciences, particularly in genetics, have provided new ways to study the molecular and cellular biology of cancer. With these tools has come new understanding of how cancers begin and develop.