A myxoma is a noncancerous tumor made of soft, jelly-like tissue that most commonly grows inside the heart. It is the most common primary heart tumor in adults, accounting for 50% to 85% of all benign cardiac tumors. While the word “myxoma” can refer to similar growths in skin or other soft tissues, the vast majority of medical attention focuses on cardiac myxomas because of their potential to obstruct blood flow or send fragments into the bloodstream.
Where Myxomas Grow
More than 75% of cardiac myxomas grow in the left atrium, the upper-left chamber of the heart. They typically attach to the wall that separates the two upper chambers, often at a small oval depression called the fossa ovalis. About 10% to 20% develop in the right atrium, and roughly 5% appear in both upper chambers at once. Tumors in the lower chambers (ventricles) are extremely rare.
The tumor cells appear to originate from multipotent stem-like cells in the heart’s connective tissue that are capable of developing into several cell types. The cells produce an inflammatory signaling molecule called IL-6, and blood levels of this molecule tend to rise and fall in step with the size of the tumor. After surgical removal, IL-6 typically drops back to normal.
Who Gets Them
Cardiac myxomas are uncommon. The estimated annual incidence is roughly 0.5 to 2 cases per million people, depending on the population studied. They are diagnosed most often between the ages of 30 and 60, with a mean age of 56 for cases that arise on their own (sporadic cases). Women are affected about twice as often as men.
A small percentage of myxomas are linked to a hereditary condition called Carney complex. In these familial cases, the average age at diagnosis drops to around 25 years. Carney complex is caused by mutations in a gene called PRKAR1A, which normally helps regulate cell growth. When this gene is faulty, cells in certain tissues proliferate unchecked, leading to myxomas in the heart and skin, along with other features like unusual skin pigmentation, hormone-producing tumors, and specific types of nerve tumors.
Symptoms and Warning Signs
Myxomas cause problems in three main ways: by physically blocking blood flow through the heart, by breaking off and traveling to other organs, and by triggering a body-wide inflammatory response.
When a myxoma partially blocks a heart valve, it can mimic the symptoms of valve disease. Shortness of breath, dizziness, fainting (especially with changes in body position), and exercise intolerance are common. Some people notice that their symptoms shift when they stand up, sit down, or roll over in bed, because the tumor can swing on its stalk and intermittently obstruct the valve opening.
Embolization, where pieces of the tumor or clots from its surface break loose and travel through the bloodstream, is the most dangerous complication. This occurs in 30% to 50% of patients with cardiac myxomas. Because most myxomas sit in the left atrium, fragments typically travel into the arteries supplying the brain, eyes, kidneys, or limbs. Stroke is sometimes the very first sign that a myxoma exists. Right-sided myxomas can send fragments to the lungs instead.
The inflammatory response driven by IL-6 can produce fever, weight loss, joint pain, fatigue, and abnormal blood test results that look like an infection or autoimmune disease. These constitutional symptoms sometimes lead to months of diagnostic uncertainty before the tumor is discovered.
How Myxomas Are Diagnosed
Echocardiography, an ultrasound of the heart, is the primary tool for detecting myxomas. A standard transthoracic echocardiogram (performed through the chest wall) can reveal a mass in the atrium, but it misses the diagnosis in roughly one in five cases. Two-dimensional imaging is far more reliable than the older single-line (M-mode) technique and successfully identified left atrial masses in all patients in a large ten-year study.
For more detailed views, a transesophageal echocardiogram (performed with a probe passed into the esophagus, closer to the heart) provides sharper images. This approach is especially useful for distinguishing a myxoma from a blood clot. Myxomas typically attach to the atrial septum by a thin stalk and move with each heartbeat, while blood clots more often form in the left atrial appendage and lack that characteristic attachment point. Getting this distinction right matters enormously: a clot is treated with blood thinners, while a myxoma requires surgery.
Surgical Removal
Surgery is the only definitive treatment for cardiac myxoma. Because of the risks of embolization, sudden obstruction, and even cardiac arrest, removal is typically performed promptly after diagnosis rather than watched over time.
The operation is done through open-heart surgery using a heart-lung bypass machine. The surgeon opens the affected atrium, identifies the tumor’s attachment site, and removes the mass along with a margin of surrounding tissue to reduce the chance of recurrence. When a tumor has a broad base on the atrial septum, the involved portion of the septum is cut away and repaired or patched. In most cases, the approach is through the left atrium alone, though some surgeons open both atria for better visibility.
Outcomes are excellent. The vast majority of patients recover fully, and the tumor does not return. For sporadic myxomas, recurrence rates are just 1% to 3%. Patients with Carney complex face a notably higher recurrence rate of up to 20%, which means they need ongoing surveillance with periodic echocardiograms for years after surgery.
Carney Complex and Familial Myxomas
If a myxoma is diagnosed in someone under 30, appears in multiple heart chambers, or recurs after surgery, Carney complex becomes a serious consideration. Diagnosing the syndrome requires meeting at least two major criteria (confirmed by imaging, biopsy, or lab tests) or one major criterion plus a supplemental one. Major criteria include cardiac or skin myxomas, characteristic freckle-like pigmentation on the lips or eyelids, certain hormone-producing adrenal or pituitary tumors, and specific testicular or thyroid abnormalities.
Genetic testing for PRKAR1A mutations can confirm the diagnosis. Because Carney complex affects multiple organ systems and runs in families, identifying it in one person often leads to screening of close relatives, potentially catching tumors before they cause symptoms.
Life After Treatment
For the large majority of patients with a one-time sporadic myxoma, surgical removal is curative. Recovery from open-heart surgery generally takes several weeks, with most people returning to normal activities within two to three months. Follow-up echocardiograms are standard practice for the first few years to confirm that the tumor has not returned.
Patients with familial myxomas or Carney complex require lifelong monitoring, not only of the heart but also of the endocrine system and skin, given the syndrome’s tendency to produce tumors in multiple locations over time.