heart cancer can be divided into two groups, primary heart cancer and metastatic heart cancer. They are rare. However, there are still reports. Most of primary heart cancer  arise from pericardium cells and endocardium cells, rarely from heart muscle cells. Metastatic heart cancer are not invasion tumors from lung cancer and are actully from distant organ. They mainly locate pericardium. Few of them locate at heart muscle

Cardiac myxomas, occuring most frequently in females, are the most common primary cardiac neoplasms, and account for the majority of all primary heart tumors.  Primary malignancies of the heart and pericardium are rare.  However, with the widespread prevalence and deployment of noninvasive imaging modalities, the occurrence of heart tumors is continuing to become evident, even though their reported detections have often been  regarded as incidental findings. NMR imaging has been applied in the diagnosis of intracardiac neoplasms. Incidence of primary heart angiosarcoma in a patient has been reported. Magnetic resonance imaging has been found to be useful in the  evaluation of tumors in the cardiac region.   

Primary malignant tumor of the heart.

Article in Acta pathologica japhttp://www.mayoclinic.org/heart-cancer/expert-answers/faq-20058130onica 32(1):101-11 · February 1982