ﻳﺤﺪﺙ ﺍﻟﺴﺮﻃﺎﻥ ﻋﻨﺪﻣﺎ ﺗﻜﺘﺴﺐ ﺧﻠﻴﺔ ﻭﺍﺣﺪﺓ ﻓﻲ ﺟﺴﻤﻚ ﻣﺠﻤﻮﻋﺔ ﻣﻦ ﺍﻟﻄﻔﺮﺍﺕ  ﺍﻟﻌﺸﻮﺍﺋﻴﺔ ﻓﻲ ﺟﻴﻨﺎﺕ ﻫﺎﻣﺔ ﺗﺠﻌﻠﻬﺎ ﺗﺒﺪﺃ ﻓﻲ ﺍﻧﺘﺎﺝ ﻧﺴﺦ ﺃﻛﺜﺮ ﻭﺃﻛﺜﺮ ﻭﺃﻛﺜﺮ ﻣﻦ ﻧﻔﺴﻬﺎ
Cancer occurs when a single cell in your body acquires a set of random mutations in important genes that cause that cell to start to produce more and more and more copies of itself.