Atrial myxoma is a benign tumor of the heart and is one of the most discussed abnormalities in cardiology. Myxomas are common topics on teaching rounds, medical conferences, textbooks, and board examinations. They have a wide variety of clinical manifestations, physical findings, and appearances on various imaging techniques. The clinical manifestations vary from fever anemia and high sedimentation rate to diastolic rumbles and “tumor plops.” The common ones are embolization and symptoms due to valve obstruction. A diastolic rumble and symptoms of exercise-induced shortness of breath as seen in mitral stenosis can be mimicked by large atrial myxomas. A diastolic rumble can be present with valve obstruction as seen in rheumatic valve stenosis, but in the case of a myxoma, a “tumor plop” is substituted for an opening snap especially when it is a left-sided tumor. Today, hearing such a sound is a rare occurrence since these tumors are often discovered earlier in the course of their natural history. “Tumor plops” are generally of a lower pitch than opening snaps.

Imaging techniques have moved the discovery of atrial myxomas earlier in their natural history. Echocardiography has played a major role in early discovery of myxoma, thus leading to resection before the dreaded embolic consequences have occurred. Computerized tomography (CT) and cardiac magnetic resonance imaging (CMRI) have also played a role in the early diagnosis of myxoma. CT scans with contrast for abnormalities such as pulmonary embolus can uncover left atrial myxomas as will be illustrated later. CMRI also has the same potential to discover these masses early in their course. Even coronary arteriography has the potential to discover an unusual coronary artery leading to a “tumor blush” with motion suggesting that is a myxoma.

Atrial myxomas have some unusual characteristics under the microscope. They contain lots of myxoid tissue and few cells. Myxomas have an endocardial lining and underneath have scarce myxoma cells that have a propensity to congregate around vascular tissue within the tumor. They have venous lake-like areas that empty into the surrounding chamber. This phenomenon can be seen in one of the following illustrations.

These benign tumors are small and usually attached to the aortic valve most commonly but sometimes attached to the mitral valve and rarely in other areas of the heart. They usually have a stalk and therefore have some mobility. Most commonly, they are single; however, as in the following example, they may be multiple. Under the microscope, they have a characteristic appearance described as a “sea anemone” in that they have hyaline material lined with endothelium. These do have embolic potential that comes to mind when these small tumors are visualized on echocardiography and have been removed surgically when this has occurred.

The following illustrations demonstrate one of these tumors at postmortem examination and one that was discovered as part of an evaluation for hypertrophic cardiomyopathy. The example of the mitral valve had embolized to the retina and was subsequently removed.¹