Heart cancer is extraordinarily rare. Primary tumors that originate in the heart show up in only 0.001% to 0.3% of autopsies, and the vast majority of those are benign growths, not cancer. When true malignant tumors do form in the heart, they are among the most aggressive and difficult-to-treat cancers. Far more commonly, cancer reaches the heart by spreading from somewhere else in the body.
Why Cancer Almost Never Starts in the Heart
Cancer develops when cells divide uncontrollably. Heart muscle cells largely stop dividing after birth, which gives them far fewer opportunities to accumulate the genetic errors that lead to cancer. Most cancers arise in tissues with high rates of cell turnover, like the skin, lungs, colon, and breast. The heart’s relative cellular stability makes it an inhospitable environment for tumor formation.
Primary vs. Secondary Heart Tumors
There are two ways a tumor can end up in the heart. A primary cardiac tumor starts in the heart tissue itself. A secondary (metastatic) tumor starts elsewhere and spreads to the heart through the bloodstream or lymphatic system. Secondary tumors are far more common. Studies have found cardiac metastases in 2% to 18% of people who died from cancer, depending on the cancer type.
The cancers most likely to spread to the heart include pleural mesothelioma (found in nearly half of cases at autopsy), melanoma (about 28%), lung cancer (18% to 21%), and breast cancer (about 16%). When someone is diagnosed with a “heart tumor,” it is almost always one of these secondary cases rather than a cancer that originated in the heart.
Benign Heart Tumors
Most primary heart tumors are noncancerous. The two most common types are papillary fibroelastomas, which are small growths that typically attach to heart valves, and myxomas, which are jellylike masses that usually grow in the left upper chamber of the heart. While benign tumors don’t invade surrounding tissue or spread, they can still be dangerous.
A myxoma can obstruct blood flow through the heart, mimicking valve disease or heart failure. Pieces of the tumor can also break off and travel through the bloodstream, causing strokes, heart attacks, pulmonary embolisms, or sudden loss of blood flow to a limb. Because of these risks, surgical removal is typically recommended even though the tumor itself isn’t cancerous. Myxomas can also cause heart valve damage, heart failure, and in rare cases, sudden cardiac death.
Types of Malignant Heart Tumors
When cancer does originate in the heart, it’s almost always a sarcoma, a type of cancer that arises from connective tissue. Sarcomas account for about 95% of malignant primary heart tumors. The most common subtype is angiosarcoma, making up roughly 30% of malignant cases. Angiosarcomas tend to develop on the right side of the heart, particularly in the right atrium, though they can affect other chambers and structures.
Other malignant types include cardiac lymphomas and pericardial mesotheliomas (cancer of the sac surrounding the heart). Lymphomas carry a somewhat better prognosis, while pericardial mesotheliomas are among the most lethal, with a median survival of just two months after diagnosis.
Symptoms and Why They’re Easy to Miss
Heart tumors produce symptoms that look like dozens of other, far more common conditions. The typical complaints include shortness of breath, chest pain, fatigue, heart palpitations, fainting spells, swelling in the legs or feet, unexplained weight loss, and low blood pressure. Some people develop fever, joint pain, or muscle aches that suggest an infection or autoimmune condition.
Because these symptoms overlap so heavily with heart failure, valve disease, and other cardiac problems, primary heart tumors are notoriously difficult to diagnose. Providers may suspect a tumor when someone develops signs of heart failure without any clear cause, but most cardiac tumors are actually discovered by accident during imaging tests ordered for something else entirely.
How Heart Tumors Are Diagnosed
An echocardiogram (ultrasound of the heart) is usually the first test to reveal a cardiac mass, but it has significant limitations. In one comparative study, echocardiography detected 28 out of 34 cardiac masses and could suggest a likely cause in only 29% of cases. Cardiac MRI detected every mass in the same study and correctly identified the probable type of tumor 75% of the time. MRI also provides better information about a tumor’s size, location, and effect on blood flow, making it the preferred tool for evaluating any mass found in the heart.
A tissue biopsy, sometimes performed during surgery, confirms whether a tumor is benign or malignant and identifies the specific cell type.
Treatment Options
Surgery is the primary treatment for most heart tumors, whether benign or malignant. Benign tumors like myxomas are typically curable with complete removal. The procedure is usually performed through the breastbone with the patient placed on a heart-lung bypass machine, and ultrasound imaging is used during the operation to verify the tumor’s exact position and confirm that heart function is intact afterward.
For malignant tumors, surgery is more complex. Complete removal is often difficult because the cancer may have grown into heart structures that can’t be replaced. In some cases, surgery is performed not to cure the cancer but to relieve symptoms, restore blood flow, or prevent dangerous complications. Chemotherapy and radiation may be used alongside surgery, and heart transplantation has been considered in select cases where the tumor can’t be resected but hasn’t spread beyond the heart.
Survival and Prognosis
Malignant primary heart tumors carry a poor prognosis. An analysis of more than 500 patients over 40 years found overall one-year survival of 46%, dropping to 22% at three years and 17% at five years. Survival has improved somewhat over time: patients diagnosed between 2000 and 2011 had a five-year survival rate of 19%, compared to 14% for those diagnosed between 1973 and 1989.
The type of tumor matters considerably. Cardiac sarcomas, the most common malignant type, have a five-year survival rate of just 11%. Cardiac lymphomas fare somewhat better at 34%. Pericardial mesothelioma has the worst outlook, with a five-year survival rate of only 9%.
Genetic Links
Most heart tumors appear spontaneously, but some are associated with inherited genetic conditions. Certain benign heart tumors cluster in families with known syndromes. For example, myxomas can run in families as part of Carney complex, a condition that also causes skin pigmentation changes and hormone-producing tumors. Rhabdomyomas, a type of benign heart tumor seen primarily in infants and children, are strongly linked to tuberous sclerosis, a genetic disorder that causes noncancerous growths in multiple organs. Cardiac fibromas have been associated with Gorlin syndrome, which also increases the risk of certain skin cancers.
When heart tumors occur as part of these syndromes, their behavior and outlook can differ from tumors that arise on their own. Genetic testing may be recommended for people diagnosed with certain cardiac tumor types, particularly if they have a family history or other features of a related syndrome.