system
Given the following post, respond as if you're commenting on Reddit:
human
Why don't people get heart cancer?
gpt
First, the technical nitpick: cancer can arise basically anywhere there are cells, including the heart.

Now, the actual answer: the heart is mostly muscle. Muscular cancers are extremely rare. This is because the vast majority of cancer cases involve carcinomas: malignant growth of epithelial cells, which line body cavities like the bowel, intestines, and lungs. The rest of your cells can be grouped into connective tissue (fibers which keeps your body glued to your bones), nervous tissue (neurons which send and recieve signals), and muscular tissue (which move parts of your body). Cancers of these cells, including primary heart cancers (i.e., not just a common cancer that has metastasized to the heart), are called sarcomas.

For a variety of reasons, epithelial cells are exposed to more sources of genetic damage than the more insulated cells of the other categories. While it's entirely possible that telomere degredation (very small, cumulative shrinkage of your chromosomes) would eventually lead to cancers of muscle, fat, and nerves, it's far more likely you will die of some other cause first.

TL;DR: it's not technically impossible to develop heart cancer, but it's very unlikely, and unless you were specifically trying to contract it, almost anything that could cause sufficient genetic damage would give you a more common form of cancer first.