system
Given the following post, respond as if you're commenting on Reddit:
human
Why is heart cancer so rare?

Edit: Thank you all for your thorough answers. This is something I've wondered about for a long time.
gpt
Heart cells are not rapidly dividing and regrowing. 
Cancer is usually present in areas where there is rapid regrowth and rapid dividing. 
Also a person with heart cancer would not live long, it would cause conduction abnormalities and improper pumping. 
For cardiac cancer where it is a met, the heart is a difficult organ to colonise, blood flow is quite fast and its difficult with all the turbulent flow to 'sit' on heart tissue.