There are over 200 types of cancer, each with its own characteristics, while congenital and environmental factors mean that the frequency of different types of cancer varies among different races and in different regions.
癌症的種類多達兩百多種，每一種癌症的特性都不相同。由於先天遺傳及後天環境的差異，不同種族、不同地區容易罹患的癌症種類也不相同。