How can people develop heart cancer?

It is very rare: Heart cancer either primary to the heart muscle or pericardium (surrounding tissue) is very rare. Even metastatic cancer from another site spreading to the heart is rare. Direct invasion of the area surrounding the heart by a nearby cancer, into the pericardium or heart muscle is unusual but more frequent than the others mentioned above.

Rarely: There are some muscle primary tumors: rhabdomyosarcoma as an example. The heart has muscle, fat, fribous tissues that can form a malignancy. Melanoma, breast, lung cancers metastasize to heart. Other cancers can spread but are less common.