Hi SilverDays and thanks for posting.

This is an interesting question and one that is quite tricky to answer.  Some cancer cells can stay dormant in the body for many years, before something triggers them to become active again.  There is research taking place into why this happens, and the causes for it are not yet fully understood. 

These cells can be present before someone finds out they have cancer.  Or they can be cells that stay in the body undetected, after treatment has happened.

Because there are over 200 types of cancer there is not one answer to this question as different cancers behave in different ways.  We do have lots of information on our website about cancer and how it starts and grows, which may help to answer your question.

I hope this is useful.

Please get back to us if you need any more information or support.  You like to talk things through with one of the nurses on our helpline.  The number to call is Freephone 0808 800 4040 and the lines are open from 9am till 5pm Monday to Friday.

Take care,

Rachel