Why Is Heart Cancer Rare? Symptoms, Causes and Treatment of Cardiac Sarcoma

Online searches for heart cancer, cardiac tumor or cardiac sarcoma may not lead you to satisfactory information—clinical trial results, meta-analyses or treatment guidelines. Instead, you will usually encounter individual case reports about these very rare cardiac tumors. In addition to symbolizing themes such as love, compassion and affection, the heart has another wonderful feature: greater resistance to cancer. Considering the heart’s importance in the body, this is a very welcome quality.

What Is a Heart Tumor? Cardiac Sarcoma

Heart cancers are very rare, and the most common among them is cardiac sarcoma. Cardiac sarcoma is a rare primary cancer of the heart (arising from the heart’s own tissue). A primary cardiac tumor is a tumor that starts in the heart. A secondary heart tumor starts elsewhere in the body and then metastasizes (spreads) to the heart. The likelihood of a cancer metastasizing to the heart is low.

Primary cardiac tumors are rare, occurring in approximately 0.001-0.3% of autopsies. In large centers, the frequency with which these tumors are encountered clinically is approximately 1 in every 500 cardiac surgery cases. Approximately 75% of primary heart tumors are benign (noncancerous) and 25% are malignant (cancerous). Approximately 75% of malignant cardiac tumors are sarcomas (soft tissue cancers).

In adults, myxoma, a benign, somewhat doughy, gelatinous type of tumor, is the most common heart tumor; in infants and children, rhabdomyomas, typically associated with tuberous sclerosis syndrome, predominate. Heart tumors can also form on the heart’s outer surface, in one or more of its chambers (intracavitary) or within its muscle tissue. Angiosarcomas, a subtype of sarcoma (soft tissue cancer), are the most common malignant primary heart tumors.

Most malignant heart tumors are secondary and arise through metastasis from primary tumors in nearby organs, such as the kidneys or lungs. If cancer has metastasized to the heart, this indicates that it is quite advanced.

Why Are Heart Tumors Rare?

Why are heart cancer and cardiac tumors so rare? The answer may lie in cardiac myocytes (heart muscle cells).

Unlike other organs, the heart appears to have little ability to repair damaged tissue. This is because the cells making up the muscle, cardiac myocytes, are highly differentiated. In other words, very early in a person’s life these cells reach the point at which they permanently exit the cell cycle and stop dividing. After that, further growth occurs through an increase in cell size rather than cell division.

This exceptionally tight control of the cardiomyocyte cell cycle acts as a double-edged sword. It not only prevents these cells from re-entering the cell cycle to reproduce and repair damaged tissue, but may also explain why they are so resistant to tumor formation.

What Are the Symptoms of Cardiac Sarcoma?

Symptoms of heart sarcoma vary depending on the tumor’s location.

• Cardiac sarcomas are most often diagnosed as angiosarcoma, and most angiosarcomas occur in the right atrium. They obstruct blood flow into or out of the heart, and this obstruction can cause symptoms such as swelling of the feet, legs, ankles and/or abdomen, and swollen neck veins. These symptoms occur because blood returning to the heart after circulating through the body cannot easily enter the right atrium or be pumped out.
• Cardiac angiosarcomas occurring in the pericardium (the thin membrane surrounding the heart) can cause fluid to increase within the membrane. If too much fluid accumulates inside the pericardial membrane, the heart’s ability to pump blood is affected, and this may lead to symptoms of heart failure, such as chest pain, shortness of breath, fatigue and palpitations.
• Small pieces of cardiac sarcomas (emboli) can break off and travel through the bloodstream to other areas of the body. An embolus may block blood flow to an organ or part of the body, causing pain and damage beyond the point where blood flow is blocked. Emboli can affect the brain (causing a stroke), lungs (causing breathing difficulties), and/or other organs and areas of the body.
• Hemoptysis (bloody sputum)
• Heart rhythm problems
• Congestion in the upper part of the face

There are also other cardiac symptoms unrelated to the tumor’s location in the heart. These may resemble symptoms of other cardiac or medical problems. Symptoms include:

• Fever
• Weight loss
• Night sweats
• Weakness (fatigue, exhaustion or feeling unwell)
• Fingers that change color or turn blue when pressure is applied (Raynaud phenomenon).
• Nail curvature with enlargement of the finger’s soft tissue.

What Methods Are Used to Diagnose Cardiac Sarcoma?

Methods for diagnosing cardiac sarcoma vary to some extent according to the symptoms present. In addition to the patient’s medical history and physical examination, diagnostic methods for cardiac sarcoma may include:

• Echocardiogram (also known as an echo): This noninvasive test uses sound waves to create an image for examining movement of the heart’s chambers and valves. Echocardiography has become the most useful tool for diagnosing cardiac sarcoma. It allows specialists to see the tumor’s exact size and location. In addition, a transesophageal echo, using a flexible tube with a transducer at its tip, is passed down the throat and esophagus. Because the esophagus lies directly behind the heart, this provides a more detailed view of the heart.
• Electrocardiogram (ECG): This test records the heart’s electrical activity, shows abnormal rhythms (arrhythmias or arrhythmias) and detects heart muscle damage. ECG changes may also indicate other heart problems, but cardiac sarcoma can cause changes in heart rhythm as well. Other diagnostic tools are therefore needed to definitively diagnose cardiac sarcoma or any other type of heart tumor.
• Computed tomography (CT): This diagnostic imaging method uses a combination of X-rays and computer technology to produce horizontal or axial images of the body (often called slices). A CT scan shows detailed images of any part of the body, including bones, muscles, fat and organs. It is more detailed than general X-rays and is used to further define the tumor’s size, location and other characteristics.
• Magnetic resonance imaging (MRI): This diagnostic method uses a combination of large magnets, radio frequencies and a computer to produce detailed images of organs and structures in the body. The images are used to further define the tumor’s size, location and other characteristics.
• Chest X-ray: This diagnostic test uses beams of electromagnetic energy to produce images of internal tissues, bones and organs on film. It can detect an enlarged heart or pulmonary congestion.
• Cardiac catheterization: In this method, also known as coronary angiography, X-rays are taken after a contrast agent (dye) is injected into an artery. The images are used to find narrowing, blockages and other abnormalities in particular arteries.
• Biopsy: This method involves removing some tissue for examination under a microscope. Other tests may indicate that a tumor is cancerous, but a biopsy is the only way to know for certain. The removed tumor sample is analyzed by a pathologist who specializes in evaluating cells, tissues and organs to diagnose disease.
• Blood tests

What Causes Cardiac Sarcoma?

The causes of tumors vary, but they are generally thought to result from abnormal regulation of cell division. Disorders of the immune system that prevent it from detecting and fighting abnormal growths can also lead to tumors. Other contributing factors include radiation, prolonged sun exposure and chemicals such as benzene.

• Related topic: What is carcinogenesis? How does a normal cell become cancerous?

What Are the Treatment Options for Cardiac Sarcoma?

Treatment options for cardiac sarcoma vary according to factors such as age, overall health, medical history, tumor location and tolerance of particular medicines. Cardiac sarcoma may also have advanced by the time symptoms begin and may often have metastasized (spread) to other areas of the body, making treatment more difficult. In general, the type of treatment depends on the tumor’s location, size and metastatic status.

Open Heart Surgery

The tumor may be removed through open heart surgery, but this is often difficult because of the tumor’s location.

Heart Transplantation

In some cases, the sarcoma has invaded the heart so extensively that it is impossible to remove completely. Heart transplantation may be attempted in these cases. However, the patient must take immunosuppressive drugs (medicines that help prevent the body from rejecting foreign tissue) after the transplant. These drugs may stimulate new sarcoma growth.

Autotransplantation

An exciting new possibility for treating cardiac sarcoma is autotransplantation. During this surgical procedure, the patient’s own heart is removed so that the tumor can be removed more completely and easily from the heart tissue. During surgery, the patient is connected to a heart-lung bypass machine, and the heart is placed back into the patient’s body after the tumor has been removed. Because the patient does not receive another person’s heart, immunosuppressive medicines are not needed. Clinical trials continue to investigate new drug treatments that may become available in this area.

In some cases, such as when cancer has spread to other areas of the body, radiation therapy or chemotherapy may be given to relieve symptoms, extend life expectancy and improve quality of life for the person.

Given how extremely rare they are, more research is needed into how and why heart tumors develop and how best to treat them.

How Can Cardiac Sarcoma Be Prevented?

As with other types of cancer, the best way to avoid cardiac sarcoma is to stay away from things that cause cancer. This greatly reduces the risk of tumors developing. Avoiding smoking or tobacco products, prolonged exposure to radiation and obesity are among the main preventive factors. 

Cancer screening, such as mammography for breast cancer, PAP smears for cervical cancer and colonoscopy for colon cancer, can detect tumors at earlier, more treatable stages. This is also a very important factor in preventing secondary cardiac sarcoma. The earlier a tumor is detected, the more likely a successful treatment outcome becomes. Finally, screening is also recommended for family members of patients diagnosed with a heart tumor.