Primary heart tumors are abnormal growths in your heart. They’re very rare. According to the European Society of Cardiology (ESC), they’re found in less than 1 out of every 2000 autopsies.

Primary heart tumors can be either noncancerous (benign) or cancerous (malignant). Malignant tumors grow into nearby structures or spread to other parts of the body (metastasize), but benign tumors don’t. Most primary heart tumors are benign. The ESC reports only 25 percent are malignant.

Some malignant tumors are:

  • sarcomas (tumors originating in connective tissue like heart muscle and fat), such as angiosarcoma and rhabdomyosarcoma
  • primary cardiac lymphoma
  • pericardial mesothelioma

Some benign tumors are:

  • myxoma
  • fibroma
  • rhabdomyoma

Secondary heart cancer has metastasized or spread to the heart from nearby organs According to the ESC, it occurs up to 40 times more often than primary cardiac tumors but is still relatively uncommon.

Cancers that spread or metastasize to the heart most often are:

Malignant heart tumors tend to grow rapidly and invade the walls and other important parts of the heart. This disrupts the heart’s structure and function, which causes symptoms. Even a benign heart tumor can cause serious problems and symptoms if it presses on important structures or its location interferes with the heart’s function.

The symptoms produced by heart tumors reflect their location, size, and structure, not specific tumor type. Because of this, heart tumor symptoms typically mimic other, more common, heart conditions like heart failure or arrhythmias. A test called an echocardiogram can almost always distinguish cancer from other heart conditions.

The symptoms of primary heart cancer can be classified into five categories.

1. Blood flow obstruction

When a tumor grows out into one of the heart chambers or through a heart valve, it can block blood flow through the heart. The symptoms vary depending on the tumor location:

  • Atrium. A tumor in an upper heart chamber can block blood flow into the lower chambers (ventricles), mimicking tricuspid or mitral valve stenosis. This might cause you to feel short of breath and fatigued, especially during exertion.
  • Ventricle. A tumor in a ventricle can block blood flow out of the heart, mimicking aortic or pulmonary valve stenosis. This can cause chest pain, dizziness and fainting, fatigue, and shortness of breath.

2. Heart muscle dysfunction

When a tumor grows into the muscular walls of the heart, they can become stiff and unable to pump blood well, mimicking cardiomyopathy or heart failure. Symptoms might include:

  • shortness of breath
  • swollen legs
  • chest pain
  • weakness
  • fatigue

3. Conduction problems

Tumors that grow inside the heart muscle around the heart’s conduction system can affect how fast and regularly the heart beats, mimicking arrhythmias. Most often, they block the normal conduction path between the atria and ventricles. This is called heart block. It means the atria and ventricles each set their own pace instead of working together.

Depending on how bad it is, you may not notice it, or you may feel like your heart is skipping beats or beating very slowly. If it gets too slow, you might faint or feel fatigued. If the ventricles start to beat rapidly on their own, it can lead to ventricular fibrillation and sudden cardiac arrest.

4. Embolus

A small piece of tumor that breaks off, or a blood clot that forms, can travel from the heart to another part of the body and lodge in a small artery. Symptoms will vary depending on where the embolus ends up:

5. Systemic symptoms

A few primary cardiac tumors can cause nonspecific symptoms, mimicking an infection. These symptoms might include:

  • fever and chills
  • fatigue
  • night sweats
  • weight loss
  • joint pain

The metastatic lesions of secondary heart cancer tend to invade the lining around the outside of the heart (pericardium). This often leads to a buildup of fluid around the heart, forming a malignant pericardial effusion.

As the amount of fluid increases, it pushes on the heart, reducing the amount of blood it can pump. Symptoms include sharp chest pain as you take a breath and shortness of breath, especially when you lie down.

The pressure on the heart can get so high that little to no blood is pumped. This life-threatening condition is called cardiac tamponade. It can lead to arrhythmias, shock, and cardiac arrest.

Doctors don’t know why some people get heart cancer and others don’t. There are only a few known risk factors for some types of heart tumors:

  • Age. Some tumors occur more frequently in adults, and others more often in babies and children.
  • Heredity. A few can run in families.
  • Genetic cancer syndromes. Most children with a rhabdomyoma have tubular sclerosis, a syndrome caused by an alteration (mutation) in the DNA.
  • Damaged immune system. Primary cardiac lymphoma occurs most often in people with a poorly functioning immune system.

Unlike pleural mesothelioma that occurs in the lining (mesothelium) of the lung, a connection between asbestos exposure and pericardial mesothelioma hasn’t been established.

Because they’re so rare and symptoms are usually the same as more common heart conditions, heart tumors can be hard to diagnose.

Tests commonly used to diagnose heart cancer include:

  • Echocardiogram. This test uses sound to create a moving image showing the structure and function of the heart. It’s the most commonly used test for diagnosis, treatment planning, and yearly follow-up.
  • CT scan. These images may help differentiate benign and malignant tumors.
  • MRI. This scan provides more detailed images of the tumor, which may help your doctor determine the type.

A tissue sample (biopsy) usually isn’t obtained because imaging can often determine tumor type, and the biopsy procedure can spread cancer cells.

When possible, surgical removal is the treatment of choice for all primary heart tumors.

Benign tumors

  • Most of these can be cured if the tumor can be completely removed.
  • When a tumor is very large or there are multiple tumors, removing part of it that isn’t inside the heart walls can improve or eliminate symptoms.
  • Some types can be followed with yearly echocardiograms instead of surgery if they aren’t causing symptoms.

Malignant tumors

  • Because they grow rapidly and invade important heart structures, they can be very difficult to treat.
  • Unfortunately, most aren’t found until surgical removal is no longer possible.
  • Chemotherapy and radiation therapy are sometimes used to try to slow tumor growth and improve symptoms (palliative care), but frequently they’re ineffective for primary heart cancer.

Secondary heart cancer

  • By the time heart metastases are found, the cancer has usually spread to other organs too and isn’t curable.
  • Metastatic disease in the heart can’t be removed surgically
  • Palliative care with chemotherapy and radiation therapy is frequently the only option.
  • If a pericardial effusion develops, it can be removed by placing a needle or small drain into the fluid collection (pericardiocentesis).

The outlook is poor for primary malignant heart tumors. One study showed the following survival rates (percentage of people alive after the given time period):

  • one-year: 46 percent
  • three-year: 22 percent
  • five-year: 17 percent

The outlook is much better for benign tumors. Another found that average survival rate was:

  • 187.2 months for benign tumors
  • 26.2 months for malignant tumors

Primary heart cancer can be a benign or malignant primary tumor or a secondary metastatic tumor. The symptoms depend on the size and location of the tumor and mimic common heart conditions.

Malignant primary heart cancer has a poor outlook but is extremely rare. Benign tumors are more common and can be cured with surgery.