Myxoma

Myxoma is a noncancerous tumor that arises from connective tissue, which is tissue that connects and supports other tissues all over the body. Most frequently, myxomas are found in the heart and are referred to as cardiac myxomas, which are the most common type of primary cardiac tumors in adults. Cardiac myxomas are usually located in the atria, which are the two upper chambers of the heart, and known as atrial myxomas. The vast majority of atrial myxomas are found in the left atrium, and are referred to as left atrial myxomas. They tend to arise from the septum, which is the wall that separates the left and right sides of the heart. Myxomas can also occur in other places in the human body, such as the skeletal muscles (i.e., intramuscular myxomas), the eye (i.e., ocular or conjunctival myxoma), and the skin (i.e., cutaneous myxoma). In general, myxoma is considered an extremely rare type of tumor. 

Benign tumors occur when cells in the body grow and divide at an excessive rate, without invading other tissues. In general, most myxomas occur sporadically, meaning that there is usually not a clear underlying cause. It is often suspected that a combination of genetic and environmental risk factors can contribute to the development of a myxoma. However, 1 in 10 cases of atrial myxoma do appear to be inherited, or passed down through families. Myxomas that are genetically inherited are called familial myxomas. 

Clinical presentations of a myxoma can vary widely depending on the location and size of the tumor. A cardiac myxoma can grow and block blood flow from the left atrium (i.e., top-left chamber of the heart) to the left ventricle (i.e., bottom-left chamber of the heart) through the mitral valve. This valvular obstruction can lead to a decrease in blood flow to the brain, which can cause syncopal episodes (i.e., fainting). Blockage of the flow through the mitral valve can also lead to a buildup of blood in the lungs, which can cause dyspnea, or difficulty breathing, and pulmonary edema, which is caused by excess fluid in the lungs. If valvular obstruction occurs at the right side of the heart (i.e., obstruction of the tricuspid valve) the individual can experience symptoms of right heart failure. With right heart failure, the right atria is unable to empty blood into the right ventricle, causing the blood to backup and result in congestion of the veins. This can present with the visible bulging of the jugular veins in the neck (jugular vein distention), enlargement of the liver and spleen (i.e., hepatosplenomegaly), and swelling of the legs (i.e., edema). 

In addition, small pieces of the myxoma can break off and travel through the bloodstream, potentially causing a blockage of an artery (i.e., embolism). If this occurs in the right side of the heart, the small pieces can travel towards the lungs and cause a pulmonary embolism, which can result in shortness of breath and chest pain. If embolism occurs from the left side of the heart, the small pieces can travel to the brain or extremities and cause a stroke or arterial embolism, respectively. Both valvular obstruction and embolisms can potentially cause sudden cardiac death. 

Additionally cardiac myxomas can interfere with the electrical signaling of the heart, and cause abnormal heart rhythms like atrial fibrillation. This can be felt as palpitations, or the feeling of extra or skipped heartbeats. In some cases of cardiac myxomas, however, individuals can be completely asymptomatic. 

The other types of myxomas often cause less severe signs and symptoms. Intramuscular myxoma, which most commonly involves the muscles of the thighs and shoulders, can present as a painless, palpable mass, which is slightly movable. Pain or neurological symptoms due to mass effect may occur. Cutaneous myxoma can present as a nodule on the face, trunk or extremities. Finally, ocular, or conjunctival, myxoma typically presents as a slow-growing, painless, yellow-pink cyst-like mass in the conjunctiva, or the membrane covering the front part of the eye.

Diagnosis of all myxomas depends on the location and size of the tumor. Regardless, diagnosis generally begins with a medical assessment of signs and symptoms. 

In individuals experiencing symptoms associated with a cardiac myxoma, a physical examination can reveal the presence of abnormal heart sounds. Blood tests might show anemia, or a lack of red blood cells. An electrocardiogram (ECG), which measures the heart’s electrical signals, may reveal atrial fibrillation. Imaging tests that can be used to diagnose cardiac myxoma include an ultrasound of the heart (echocardiogram), chest X-rays, computerized tomography (CT) scans, or magnetic resonance imaging (MRI). An echocardiogram can be used to detect the presence and location of the tumor and evaluate its mobility. Chest X-rays might reveal cardiomegaly (i.e., heart enlargement), calcification of the tumor, evidence of valvular obstruction, or pulmonary edema. A CT scan or MRI can visualize the cardiac tumor and its movement within the heart. 

Intramuscular myxomas are also often visualized using ultrasound imaging, CT scans, or MRI. They are usually confirmed with a biopsy and pathological examination of the suspected tumor. Similarly, ocular and cutaneous myxomas are usually confirmed with a biopsy. 

Myxomas can be removed through surgical intervention. With a cardiac myxoma, open heart surgery is performed to remove the tumor. The atrial septum, or the wall that separates the left and right upper chambers of the heart, may also be removed depending on the depth of tumor penetration. The pericardium, which is a two-layered membrane that covers the heart, can be used to repair the atrial septum. In cases where the myxoma extends into the mitral valve, individuals may need to have the valve replaced. In rare instances, myxomas can reoccur if the tumor is not removed completely during surgery.

Intramuscular myxomas can be also removed through surgical excision, after which recurrence of the tumor is rare. Similarly, ocular myxomas undergo complete removal and rarely recur. On the other hand, cutaneous myxomas frequently reform, even after surgical removal.