After an initiating event, when does a cell become cancerous? if it evades of the body's control mechanisms.

If it evades all of the body's control mechanism

Explanation:

Mutation occurs when there is any change in the sequence of nucleotides. All mutations are not cancerous. It is an initiating event and the body has a mechanism to correct some mutation or do cell apoptosis.  

When the mutation is not controlled by cell and it evades all of the body's control mechanism than the mutation converts into cancer and the cell is called a cancerous cell.  

Then the cell can not go apoptosis and get the ability to grow uncontrollably and invade in different tissue. This property of the cancerous cells is called metastasis.

the denominator has a very specific role.