I dont know the inner workings of the body... but I try to learn from nature.
I know that Nature has natural movements and cycles... and everything must be in motion of one sort or another. So if an organ becomes unbalanced/full of undesirables and whatnot... to the point where it cannot cannot support the flow of in and out. The environment changes... it becomes stagnant... and decay begins. Much like a swamp vs. a fresh lake.
I was thinking about what you said that cancer is a rotting against healthy flesh. and that maybe cancer is the bodies healing mechanism... to be a barrier for the healthy flesh. And a way to help re-establish the flow of life in that particular organ or area again.
I cannot say for sure... but I do know that nature does not make mistakes. And cancer hardly seems like a mistake, it is a result. And your statement that cancer is the result of rotting against healthy flesh makes a world of sense.