The heart is a powerful muscle that pumps blood, circulating oxygen and nutrients throughout the body. The question of whether cancer can affect this organ has a clear, though nuanced, answer. Heart cancer, or a tumor originating in the heart, is an extremely rare occurrence in medical practice. While masses can develop in the heart, the overwhelming majority of growths found there are not malignant.
Why Primary Heart Cancer Is Extremely Rare
The heart’s resistance to cancer stems from the exceptionally low rate of cell division in its muscle tissue. Adult heart muscle cells, known as cardiomyocytes, are terminally differentiated, meaning they rarely undergo mitosis or cell replication after birth. Since cancer is a disease of uncontrolled cell division, this lack of proliferation significantly reduces the opportunity for DNA replication errors to accumulate. Organs with high cell turnover, such as the skin, lungs, or colon, are statistically far more likely to develop malignant tumors.
When a malignant tumor originates within the heart tissue, it is classified as a primary heart cancer. Nearly all primary heart cancers are a type of sarcoma. The most common subtype in adults is angiosarcoma, which often arises in the right atrium. This cancer is aggressive but accounts for less than 0.03% of all cancers diagnosed.
The Clinical Reality: Secondary Heart Tumors
When a malignant tumor is discovered in the heart, it is almost always a secondary, or metastatic, cancer. This means the cancer began in a different organ and then spread to the heart through the bloodstream or lymphatic system. Metastatic heart tumors are estimated to be 20 to 30 times more frequent than those that start in the heart itself.
Cancers with a high propensity to spread to the heart include those originating in the lungs, breast, and malignant melanoma. Cancer cells can also reach the heart by direct extension from neighboring structures, such as the esophagus or lung. Therefore, a malignant heart mass is most often a sign of advanced systemic disease rather than a condition beginning in the cardiac muscle.
Common Non-Malignant Heart Masses
The vast majority of masses found in the heart are non-cancerous, or benign. The most common primary heart tumor overall is the cardiac myxoma, which accounts for approximately half of all primary growths. Myxomas typically develop in the left atrium.
While myxomas are not cancerous, they pose a serious health risk due to their location and mobility. These masses can block the flow of blood through the heart valves, mimicking symptoms of heart failure or causing sudden death. Fragments of the tumor can also break off and travel through the bloodstream (embolism), potentially causing a stroke or other circulatory complications. Other benign tumors include fibromas and rhabdomyomas, which are more common in infants and children.
Diagnosis and Treatment Approaches for Heart Tumors
The symptoms that prompt investigation into a heart tumor are often non-specific, frequently mimicking other common heart conditions. Patients may experience sudden shortness of breath, an irregular heartbeat (arrhythmia), or signs of heart failure like swelling in the legs. These ambiguous symptoms necessitate a thorough diagnostic workup.
The initial and most common diagnostic tool is an echocardiogram, a specialized ultrasound that provides real-time images of the heart’s structure and motion. If a mass is identified, physicians use further imaging, such as Cardiac CT or Cardiac MRI, to characterize the tumor’s size, location, and likely composition. A definitive diagnosis, especially for suspected malignant tumors, often requires a tissue sample obtained through a biopsy.
Treatment depends on the tumor type and origin. Benign tumors like myxomas are generally treated with prompt surgical removal to prevent obstruction or embolization. For the rare primary malignant tumors, treatment may involve a combination of surgery, chemotherapy, and radiation therapy. In cases of secondary metastatic tumors, the strategy focuses primarily on addressing the original cancer, with heart involvement often dictating palliative care due to the advanced stage of the disease.