Probably due to 'repair' needs, but I've no proof of that, cancer is, after all, a 'mis'sed-function of repair activity...
Cancer typically occurs in tissue where cells are reproducing. Since muscle cells generally do not reproduce, there is less chance of cancer.
Read my thread on "Heart cancer?" Your post's similarity indicates you have.
Cancer is a symptom of accumulation of mutations in a cell. Every round of mitosis more mistakes are incorporated into your genome, also such cells are more sensitive to chemical or radiological disturbances. In an actively dividing cell, it can thus cause the overgrowth by lack of inhibition signals that would normally control and stop overgrowth. Due to this uncontrolable growth, more mistakes will happen and even whole chromosomes will be lost.
In non-diving tissue, there is no expression of growth signals, so even though some mutations might occur due to radiation, it won't have much effect.
Loren, I had actually wondered about this before I read your thread, and when I looked at your thread it seemed specifically to be describing why heart tissue wasn't prone to cancer.
Now that I've got an answer, I'm curious why organ tissue divides more often than muscle tissue.
Sorry if I seemed overly proprietary or blunt. I probably was.
Cancer of neuronal brain cells is also extremely rare if I am not entirely mistaken. Brain tumours originate usually from the supportive tissue.
Nah, don't worry about it, rational assumptions are part of being human.
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