Secondary heart cancer, gross specimen . Heart slice with metastatic malignant (cancerous) carcinomas (invasive tumours, light areas). A metastatic tumour is a secondary cancer that has spread (metastasised) from the site of the original cancer. Secondary heart tumours, although more common than primary tumours, are uncommon. Small single tumours can sometimes be removed surgically, however, once a cancer has spread to the heart the prognosis is poor.