- An uncommon but important differential diagnosis of cardiac masses.
- Diagnosis is suspected by history, physical examination, and
imaging characteristics and confirmed by biopsy of mass.
Cardiac tumors arise either as a primary tumor of the heart or more commonly from metastasis of a distant noncardiac primary tumor. Because of the low incidence and nonspecific clinical manifestations, cardiac tumors have often been diagnosed incidentally during evaluation of a seemingly unrelated problem or misdiagnosed as other cardiac
conditions. A high index of suspicion in combination with characteristic cardiovascular
imaging study are essential for rapid identification of cardiac tumors.
Metastatic Cardiac Tumors
Metastatic cardiac tumors are about 40 times more common than primary tumors. Cardiac metastases occur in approximately 5% of
patients who die of malignant tumors and are often present as pericardial
effusions; myocardial, coronary, and intracavitary involvement occurs
with less frequency. The tumor that most often metastasizes to the
heart is disseminated malignant melanoma, which occurs in 50–65% of
afflicted patients. Other tumors with high predilection for cardiac
metastasis are bronchogenic carcinoma, breast cancer, renal cell
carcinoma, mesothelioma (by direct extension or hematogenous spread),
and lymphoma and leukemia (by lymphatic spread). Rarely, adenocarcinoma
of the colon can metastasize to the heart by lymphatic or hematogenous spread,
usually affecting first the pericardium and then the myocardium.
Cardiac metastases that occur in patients with colon cancer are
usually preceded by involvement of other organs. Metastases to the
endocardium have been reported in renal cell carcinoma, adenocarcinoma of
the stomach, laryngeal carcinoma, pancreatic cancer, and mucinous
adenocarcinoma of the cecum and of the ovary. Renal cell carcinomas
can extend into the inferior vena cava, and the tumor thrombus occasionally
involves the right atrium (Figure 30–1).
Transthoracic echocardiogram in a 65-year-old man with a history of renal cell carcinoma in whom dyspnea and lower extremity edema developed. A: The apical four-chamber view shows a large mass most likely representing metastatic renal cell carcinoma in the right atrium. B: During diastole, the tumor prolapses through the tricuspid valve. LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle; TV, tricuspid valve.
Primary tumors of the heart are rare, with an incidence from 0.001% to 0.28% reported in unselected autopsy studies. Although myxoma is the most frequent tumor type in adults, rhabdomyomas represent the most common type in the pediatric population.
The majority (75–80%) of primary cardiac tumors are benign and therefore potentially curable (Table 30–1).
Table 30–1. Primary Cardiac Neoplasms.
| Save Table
Table 30–1. Primary Cardiac Neoplasms.
|Malignant fibrous histiocytoma|
|Benign or Malignant|
McAllister HA, Hall RJ, et al. Tumors of the heart and pericardium. Cur Probl Cardiol. 1999;24:57–116.
These tumors account for approximately half of benign cardiac tumors and are usually found in patients between 30 and 60 years old, with a mean age of onset of 51 years. They occur predominantly in women;
although most are isolated or sporadic, they can also be familial
or complex. Less than 10% of myxomas are familial and are apparently
transmitted in an autosomal-dominant pattern. Familial myxoma presents
earlier in life, with a mean age of onset of 25 years. Complex cardiac
myxomas or the familial Carney complex may include such features
as multiple pigmented skin lesions (lentigines), myxoid fibroadenomas
of the breast, tumors of the pituitary and testes, and primary pigmented
nodular adrenocortical disease. Carney complex appears to be genetically
heterogenous with gene localization on chromosome 2p16 and chromosome
17q24. The majority of Carney complex appears to be caused by a mutation
in the PRKAR1α gene that encodes
the R1α regulatory subunit of the cyclic adenosine
monophosphate-dependent protein kinase A (PKA). Patients with familial
or complex myxomas are more likely than those with sporadic myxomas
to have multiple (30–50%) and recurrent (12–22%)
tumors. This occasional recurrence of myxomas and a few reported
cases of invasion of surrounding tissue by the tumor suggest that
myxomas have some low-grade malignant features.
Macroscopically, myxomas are pedunculated and gelatinous in consistency; the surface may be smooth, irregular, or friable. Friable or villous, myxomas are associated with a higher risk of embolization, whereas
larger tumors with a smooth surface tend to present with obstructive
cardiovascular symptoms. Microscopically, myxoma is characterized
by islands of tumor cells with variable shapes, round, elongated,
or polyhedral scattered throughout pale staining extracellular matrix.
The tumor cells are thought to be derived from mesenchymal cardiomyogenic precursor cells.
Most myxomas (74%) occur in the left atrium, although they can occur in any chamber (right atrium, 18%; right ventricle, 4%; left ventricle, 4%) or on any valve. They often arise from the endocardial surface of the left atrium with a stalk attached to the interatrial septum close to the fossa ovalis (Figure 30–2). When a myxoma occurs in the ventricles, it almost always originates from the free wall. Although asymptomatic myxomas have been recognized, most patients experience one or more effects from the classic triad of constitutional, embolic, and obstructive manifestations. (For details, refer to the section on Clinical Findings.)
Transthoracic echocardiogram in an apical four-chamber view showing a mass in the interatrial septum. The mass was resected and found to be an atrial myxoma.
Kirschner LS et al. Mutations of the gene encoding the protein kinase A type I-alpha regulatory subunit in patients with ...