I'm having a conceptual nightmare trying to understand when a group of cells may become cancerous and the more resources I consult the more confused I seem to get.

In order for a cell to become cancerous, does it have to mutate to knock out tumour suppressor genes and have a proto-oncogene become an oncogene?

I'm currently working on the basis that that is the case, or at least that a mutated TSG on its own will not cause uncontrolled division. However wikipedia seems to suggest that an oncogene alone can cause uncontrolled division with a functional TSG in place.

It could be a flaw in the idea I have that tumour suppressor genes only trigger apoptosis once a cell has started to divide rapidly, are they actually carrying it out to a regular schedule independent of oncogene presence?