It is interesting to note that patients with cardiac tumors may initially have no symptoms or physical findings but exhibit abnormalities on imaging. Alternatively, there may be a host of nonspecific symptoms or findings on physical examination, and of course, there may be very specific and detailed symptoms or signs that should alert physicians to the possibility of a cardiac tumor (Table 85-1). The most important consideration in confirming the presence of a cardiac tumor is a high index of suspicion and integration of the symptoms, findings on physical examination, and imaging characteristics in a logical way to establish a clinically reasonable plan of action.

The initial evaluation is typically an imaging test such as two-dimensional echocardiography¹ or magnetic resonance imaging (MRI)^2,3 in which a mass is identified. Depending on the characteristics of this mass and the known comorbid conditions of the patient, additional imaging may be undertaken, including three-dimensional echocardiography with contrast enhancement,⁴ MRI with gadolinium,^5,6 coronary angiography to define the presence of coronary artery disease,⁷ position emission tomography (PET) to provide staging for cancer,⁷ or computed tomography (CT) to clarify intrathoracic structures.^8,9 Transesophageal echocardiography (TEE) can also provide very specific anatomic information that is critical to planning treatment (Table 85-2).⁷

When assessing a cardiac mass as initial evaluation for a cardiac tumor, the clinical context in which the image was obtained is critical because the differential diagnosis of a cardiac mass is broad and includes tumors, thrombi, infection, and artifacts (Table 85-3). For example, if two-dimensional echocardiography shows an apical mass in a patient with new-onset heart failure, a cardiac tumor is less likely.¹⁰ The presence of a severe wall motion abnormality, as well as the fact that the mass may appear distinct from the myocardial wall and is lobulated, strongly suggests that the mass is much more likely to be a thrombus than a tumor (Fig. 85-1). Another scenario involves a patient with a history of melanoma that is metastatic to other organs and on routine cardiac imaging a solid mass is seen in an unusual location. Because there is no wall motion abnormality and no significant valvular disease or clinical signs suggestive of infective endocarditis, this mass is very likely to be a metastatic lesion to the heart (Fig. 85-2). A common consideration that may suggest a tumor, in regard to imaging, is movement of the mass and related structures during a motion image. If a tumor is infiltrating the myocardium, the involved myocardial area will not contract in normal fashion. A left ventricular myocardial apical mass contracting similar to that of surrounding tissue is likely to be either focal hypertrophy (Fig. 85-3) or left ventricular noncompaction^11,12 (Fig. 85-4) as opposed to a cardiac tumor (Fig. 85-5). Furthermore, progression of an image over time may also indicate the pathologic process. If a cardiac mass changes in size from one image to the next, suspicion of a cardiac tumor is much higher. However, if an apical mass is stable for months or years, it is very unlikely to be a cardiac tumor. Of course, the exact nature and location of a mass are critical in determining whether it is likely to be a tumor.¹³ A classic example of this principle is lipomatous hypertrophy of the intra-atrial septum (Fig. 85-6A, B). The initial suspicion might be a myxoma or other tumor, but TEE revealing specific characteristics that are a hallmark of lipomatous hypertrophy will confirm the diagnosis.¹⁴

Most (>80%) primary cardiac tumors are benign, and myxoma is by far the most common.^15,17 Myxoma constitutes about 50% of all benign cardiac tumors in adults, but only a small percentage of such tumors in children.¹⁸ Rhabdomyoma is the most common benign tumor in children and accounts for 40% to 60% of cases.¹⁷ Other benign cardiac tumors that have been described include fibromas, lipomas, hemangiomas, papillary fibroelastomas, cystic tumors of the atrioventricular node, and paragangliomas. The remaining 20% of primary cardiac tumors are malignant and usually described pathologically as sarcomas.^19–21

Myxomas

Most myxomas (>80%) are found in the left atrium and in decreasing frequencies in the right atrium, right ventricle, and left ventricle. The incidence of cardiac myxoma peaks at 40 to 60 years of age, with a female-to-male ratio of approximately 3:1.²⁰ Most myxomas occur sporadically but may be familial, and occasionally they have been described in relation to a particular syndrome called the Carney complex, an autosomal dominant condition associated with cardiac myxomas, myxomas in other regions (cutaneous or mammary), hyperpigmented skin lesions, hyperactivity of the adrenal or testicular glands, and pituitary tumors. The Carney complex occurs at a younger age and should be considered when cardiac myxomas are discovered in atypical locations in the heart.¹⁹

Cause and Pathophysiology

The exact origin of myxoma cells remains uncertain, but they are thought to arise from remnants of subendocardial cells or from multipotential mesenchymal cells in the region of the fossa ovalis that can differentiate along a variety of cell lines. The hypothesis is that cardiac myxoma originates from a pluripotential stem cell and the myxoma cells express a variety of antigens and other endothelial markers. Myxomas typically form a pedunculated mass with a short broad base (85% of myxomas), but sessile forms can also occur.¹⁵ Classically, myxomas appear yellowish, white, or brownish and are frequently covered with thrombus (Fig. 85-7). Tumor size can range from 1 cm to larger than 10 cm, and the surface is smooth in most cases (Figs. 85-8 and 85-9). Myxomas may have a surface that consists of multiple fine or very fine villous, gelatinous, and fragile extensions that have a tendency to fragment.¹⁵ Histologically, myxomas are composed of spindle- and stellate-shaped cells with myxoid stroma that may also contain endothelial cells, smooth muscle cells, and other elements surrounded by an acid mucopolysaccharide substance. Calcifications may also be seen in some cases.¹⁵