the best heart centers near me What is a cardiac tumor ? A cardiac tumor is an abnormal growth of tissue in the heart, and may be classified as either cancerous (malignant) or non-cancerous (benign). Cardiac tumors are further classified as either primary secondary (spread from a primary tumor in a different part of the body). Primary cardiac tumors are extremely rare, occurring in approximately 1 in 3000 individuals. Seventy-five percent of primary cardiac tumors are benign. Secondary cardiac tumors are 20-30 times more frequent than primary cardiac tumors and most commonly arise in patients with lung cancer, breast cancer, melanoma, renal cell cancer.