Practice Essentials
Primary cardiac neoplasms are rare entities, [1, 2, 3] with an autopsy prevalence of 0.001-0.28%. The most common primary malignant tumor of the heart and pericardium is sarcoma. With the publication of the 4th edition of the WHO Classification of Tumours of the Lung, Pleura, Thymus and Heart, cardiac sarcomas are now classified as follows [4] :
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Angiosarcoma
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Undifferentiated pleomorphic sarcoma
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Osteosarcoma
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Myxofibrosarcoma
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Leiomyosarcoma
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Rhabdomyosarcoma
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Synovial sarcoma
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Miscellaneous sarcomas
Among the changes from the 3rd edition, cardiac sarcomas with a predilection for the left atrium (the most common site in the heart), have been simplified. This group of sarcomas previously included low-grade lesions (fibrosarcoma, myxofibrosarcoma, myxosarcoma, fibromyxosarcoma), and intermediate- to high-grade lesions (myxoid malignant fibrous histiocytoma, malignant fibrous histiocytoma). High-grade sarcomas are now classified as undifferentiated pleomorphic sarcoma to conform with the WHO classification of soft-tissue tumors. The older designations of the lower-grade sarcomas have also been combined under the classification of myxofibrosarcoma. [4]
Another change in classification of cardiac sarcomas is that of tumors with bone matrix formation. In the third edition, sarcomas with osteosarcoma or chondrosarcoma were classified as a subtype of undifferentiated pleomorphic sarcoma. Partly to conform to the WHO classification of soft-tissue tumors, the current edition places these tumors in a separate category of osteosarcoma analogous to extraskeletal osteosarcomas of the soft tissue. [4]
The diagnosis of cardiac sarcoma is often not made preoperatively or even antemortem. It is overlooked because of the rarity of the lesion and the nonspecific nature of the symptoms and signs. Tumors that originate in the epicardium or pericardium and that lead to cardiac encasement may cause chest pain, hypotension, tachycardia, and malaise. Diminished cardiac sounds and a friction rub may be heard.
Cardiac tamponade (usually from a persistent and bloody pericardial effusion) may eventually cause intractable cardiac failure. Myocardial involvement may lead to refractory arrhythmias, heart block, heart failure, angina, or infarction. Endomyocardial masses cause valvular obstruction or insufficiency. Rarely, a pedunculated tumor causes an audible plop from tumor prolapse through a valve. Tumor fragments may embolize from the right side of the heart to the lungs and cause dyspnea or hemoptysis. Left-sided emboli may lead to cerebrovascular accidents, peripheral organ infarctions, seizures, and distant metastases. Local extension of tumors may cause signs and symptoms such as superior vena cava syndrome, hemoptysis, and dysphonia.
Pathophysiology
Cytogenetic analysis of these tumors may show numerical and structural chromosomal changes. Immunohistochemical analysis has revealed, in the case of a cardiac angiosarcoma, high expression of mutated p53 gene products. [5]
Angiosarcoma
Nearly 80% of cardiac angiosarcomas arise as mural masses in the right atrium. Typically, they completely replace the atrial wall and fill the entire cardiac chamber. They may invade adjacent structures (eg, vena cava, tricuspid valve).
On cardiac magnetic resonance imaging, angiosarcoma appears as a heterogeneous, nodular mass in the right atrium, and grossly, there are invariably areas of hemorrhage.
These tumors are both symptomatic and rapidly fatal. Extensive pericardial spread and encasement of the heart often occur. Pericardial angiosarcoma (without myocardial involvement) occurs rarely.
Rhabdomyosarcoma
Rhabdomyosarcomas are derived from striated muscle and are rare, accounting for 0% to 5% of primary cardiac sarcomas. Most cases appear in children, at a mean age of approximately 14 years. Rhabdomyosarcoma has a predilection for the ventricle and the histologic features are usually of the embryonal subtype. [6]
Myxofibrosarcoma and undifferentiated pleomorphic sarcoma
Together, this group of tumors that occur primarily in the left atrium account for at least 50% of cardiac sarcomas. A small proportion of undifferentiated pleomorphic sarcomas occur in other chambers, most frequently the left ventricle and right atrium.
Histologically, these tumors are heterogeneous, ranging from bland collagen-rich areas that may in small samples appear benign to low-grade sarcomas with myxoid background to areas of high pleomorphism and mitotic activity (undifferentiated pleomorphic sarcoma). [6]
These whitish lesions have a firm texture and exhibit infiltrative growth patterns. Myxofibrosarcoma may have a better prognosis than does undifferentiated pleomorphic sarcoma.
Tumors of the pericardium
Sarcomas of the pericardium are rare; the most common are synovial sarcoma (which also accounts for approximately 5% of cardiac sarcomas), angiosarcoma (which often involves both the pericardium and right atrium), and undifferentiated pleomorphic sarcoma.
Metastatic cardiac sarcoma
Metastases to the heart and pericardium are 40 times more common than primary cardiac tumors. In fact, an estimated 25% of patients who die from metastatic soft tissue sarcoma have cardiac metastases. No particular gross pattern of myocardial spread exists (ie, diffuse, nodular). In children, rhabdomyosarcoma is the most common type of sarcoma that metastasizes to the heart.
Epidemiology
Cardiac sarcoma occurs in less than 0.2% of decedents undergoing autopsy, both nationally and internationally. [7] Sex predilection has not been defined for cardiac sarcoma. Cardiac sarcomas can occur at any age; however, children have an increased rate of cardiac rhabdomyosarcomas.
Prognosis
Data from one series of patients with primary cardiac sarcomas showed that median survival is approximately 17 months for those who undergo complete surgical excision and 6 months for those who do not. [8]
Patients with angiosarcoma had a lower survival compared with patients with other histologies and longer survival is associated with left-sided lesions. [9]
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Angiosarcoma of the heart, with pericardial encasement by hemorrhagic tumor. Image courtesy of Dr. K. Marchant.
