Primary Pericardial Tumors · 1616 October Special Issue 2013 radiographics.rsna.org Figure 3. Acute inflammation in a chronically inflamed pericardial cyst. Contrast-enhanced CT

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1613CARDIAC NEOPLASMS

Carlos S. Restrepo, MD • Daniel Vargas, MD • Daniel Ocazionez, MD Santiago Martínez-Jiménez, MD • Sonia L. Betancourt Cuellar, MD Fernando R. Gutierrez, MD

Primary pericardial tumors are rare and may be classified as benign or malignant. The most common benign lesions are pericardial cysts and li-pomas. Mesothelioma is the most common primary malignant pericardial neoplasm. Other malignant tumors include a wide variety of sarcomas, lymphoma, and primitive neuroectodermal tumor. When present, signs and symptoms are generally nonspecific. Patients often present with dyspnea, chest pain, palpitations, fever, or weight loss. Although the imaging ap-proach usually begins with plain radiography of the chest or transthoracic echocardiography, the value of these imaging modalities is limited. Cross-sectional imaging, on the other hand, plays a key role in the evaluation of these lesions. Computed tomography and magnetic resonance imaging allow further characterization and may, in some cases, provide diagnostic findings. Furthermore, the importance of cross-sectional imaging lies in assessing the exact location of the tumor in relation to neighboring struc-tures. Both benign and malignant tumors may result in compression of vi-tal mediastinal structures. Malignant lesions may also directly invade struc-tures, such as the myocardium and great vessels, and result in metastatic disease. Imaging plays an important role in the detection, characterization, and staging of pericardial tumors; in their treatment planning; and in the posttreatment follow-up of affected patients. The prognosis of patients with benign tumors is good, even in the few cases in which surgical intervention is required. On the other hand, the length of survival for patients with ma-lignant pericardial tumors is, in the majority of cases, dismal.©RSNA, 2013 • radiographics.rsna.org

Primary Pericardial Tumors1

ONLINE-ONLY SA-CME

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LEARNING OBJECTIVES

After completing this journal-based SA-

CME activity, partic-ipants will be able to:

■ Recognize the im-aging characteristics of a wide array of primary pericardial tumors.

■ Describe the sa-lient clinical features of the most com-mon primary peri-cardial tumors.

■ Discuss the role of the radiologist in the care of patients with primary pericardial tumors.

Abbreviations: ADC = apparent diffusion coefficient, MIBG = metaiodobenzylguanidine, PET = positron emission tomography

RadioGraphics 2013; 33:1613–1630 • Published online 10.1148/rg.336135512 • Content Codes: 1From the Department of Radiology, University of Texas Health Science Center, San Antonio, Tex (C.S.R.); Mallinckrodt Institute of Radiology, Washington University School of Medicine, Barnes-Jewish Hospital, St Louis, Mo (D.V., F.R.G.); Department of Radiology, University of Washington, Seattle, Wash (D.O.); Department of Radiology, Saint Luke’s Hospital, Kansas City, Mo (S.M.J.); and Department of Diagnostic Radiology, University of Texas M.D. Anderson Cancer Center, Houston, Tex (S.L.B.C.). Recipient of a Certificate of Merit award for an education exhibit at the 2012 RSNA Annual Meeting. Received March 18, 2013; revision requested May 9 and received June 3; accepted June 24. For this journal-based SA-CME activity, the author S.M.J. has disclosed a financial relationship (see p 1628); the other authors, editor, and reviewers have no relevant relationships to dis-close. Address correspondence to D.V., Department of Radiology, University of Colorado, Denver, Colo (e-mail: [email protected]).

©RSNA, 2013

1614 October Special Issue 2013 radiographics.rsna.org

IntroductionPrimary cardiac neoplasms are rare, with a preva-lence of approximately 0.02%–0.056% (1,2); however, those arising primarily from the pericar-dium are even less common. Meng et al (3) and Patel et al (4) determined that primary pericar-dial neoplasms accounted for only 6.7%–12.8% of all primary tumors arising in the cardiac re-gion. On the basis of these data, the prevalence of primary pericardial neoplasms ranges from about 0.001 to 0.007%. Neoplastic involvement of the pericardium by direct invasion or metastatic dis-ease is, on the other hand, 100–1000 times more prevalent (5). The most common benign pericar-dial mass is a pericardial cyst, followed by lipoma. Mesothelioma is the most common primary pericardial malignancy. Other primary malignant neoplasms include a wide variety of sarcomas as well as lymphoma (4).

The patient’s clinical history is highly valuable in narrowing the differential diagnosis. In patients with known neoplastic disease, a pericardial le-sion will most likely be metastatic. Pericardial fibrosis may be seen in patients who have under-gone irradiation of the chest. In patients with a history of sternotomy, a hematoma or infectious process may manifest as a mass. In addition, diffuse processes such as pericarditis may also mimic a neoplasm.

Patients with primary pericardial neoplasms present with diverse symptoms. Clinical signs and symptoms are usually the result of associated pericardial effusion, pericarditis, or invasion of adjacent structures and are therefore nonspecific. Symptoms include exertional dyspnea, chest pain, cough, palpitations, fatigue, night sweats, fever, and facial or lower-extremity edema. Oc-casionally, a primary pericardial tumor may be found incidentally in an asymptomatic patient, during work-up for an unrelated illness (5–8).

With such a broad spectrum of clinical symp-toms and findings, imaging plays an important role in the evaluation of patients with primary pericardial neoplasms. Most often, the diagnostic approach begins with plain radiography of the chest or transthoracic echocardiography. Ra-diographic findings include an enlarged cardiac silhouette, an abnormal mediastinal contour, or a discrete mediastinal mass (5). Echocardiogra-phy, although commonly performed, has a lim-

ited role in the evaluation of primary pericardial neoplasms. Frequently, the only finding may be a thickened pericardium or pericardial effusion. Transesophageal echocardiography offers in-creased sensitivity compared with transthoracic echocardiography and may be a useful tool (8). Inherent limitations to this modality include its invasiveness and its limitations in the assessment of structures that are distant to the transducer, including the mediastinum, diaphragm, and lung parenchyma. Computed tomography (CT) dem-onstrates the location of the tumor, its relation-ship with neighboring structures, and its invasion of vital structures. CT also aids in narrowing the differential diagnoses, as some of these lesions may be characterized on the basis of their attenu-ation values or pattern of enhancement. In ad-dition, CT can help confirm the presence of lo-coregional or distant metastatic disease. Magnetic resonance (MR) imaging provides higher contrast resolution compared with CT and, as a result, is a more powerful tool for characterizing the lesion. Another advantage of MR imaging is its ability to demonstrate myocardial invasion, as well as give insight into the functional impact of the neo-plasm (5,8–11). Positron emission tomography (PET)/CT may be useful as a staging tool, as it may demonstrate distant or locoregional spread of disease (12).

Although in most cases the diagnosis of a primary pericardial tumor is ultimately reached through tissue sampling, knowledge of the sa-lient characteristics is fundamental for the radi-ologist to offer a pertinent differential diagnosis on the basis of imaging appearance, because clinically, many of these lesions behave similarly. The radiologist also plays an important role in assessing the resectability of these lesions and evaluating the patient for associated complica-tions. Some of the commonly seen complica-tions include invasion of mediastinal structures, regional or distant metastases, pericardial effu-sion, cardiac tamponade, compression of vascu-lar structures or cardiac chambers, encasement of vital structures, involvement of coronary ar-teries, myocardial infarction, diastolic dysfunc-tion, and constrictive physiology.

In this article, the spectrum of primary pericar-dial tumors is discussed, with emphasis on their imaging features, the patients’ clinical presenta-tion, and the wide array of associated cardiovascu-lar complications.

RG • Volume 33 Number 6 Restrepo et al 1615

Figure 1. Pericardial cyst. (a) Contrast material–enhanced CT image of the chest demonstrates a well-defined lesion of fluid attenuation in the right anterior cardiophrenic angle. (b) Coronal T2-weighted MR image shows the well-defined hyperintense lesion in the right anterior cardio-phrenic angle.

Pericardial CystPericardial cysts, also called mesothelial cysts of the pericardium, are congenital lesions that arise as a result of aberrant formation of the somatic cavities (13). These cysts are usually unilocular, and the cyst walls are lined with a single layer of mesothelial cells, whereas the remainder of the wall is composed of a thicker layer of connective tissue (14). Most commonly, pericardial cysts are located in the right anterior cardiophrenic angle, with the next most frequent location being the left anterior cardiophrenic angle. Occasion-ally, a pericardial cyst may arise elsewhere in the mediastinum (13). In more than half of the cases, pericardial cysts result in no symptoms. When present, patients’ symptoms are often vague and include chest pain, cough, fever, and arrhythmias (15). Symptoms may also result from compres-sion of adjacent structures. Serious complications are rare, but they may include erosion into vas-cular structures, pericarditis, obstruction of the right ventricular outflow tract, pulmonary steno-sis, or sudden death (15).

Pericardial cysts are most often found inciden-tally at chest radiography or echocardiography. At chest radiography, a pericardial cyst appears as a well-defined, smooth, anterior mediastinal mass. Echocardiography demonstrates the cystic nature of this lesion (13,14).

CT and MR imaging are better at character-izing a pericardial cyst and its relationship with

adjacent structures. Typically, pericardial cysts appear on CT images as well-defined, nonen-hancing, homogeneous fluid-attenuation lesions that contain no internal septa (16). Occasion-ally, the cyst may contain proteinaceous fluid, in which case the lesion will demonstrate interme-diate attenuation at CT. Pericardial cysts with hemorrhagic contents appear with hyperattenu-ation at CT.

MR imaging offers further characterization of the internal contents of the cysts. Usually, pericardial cysts demonstrate intermediate to low signal intensity on T1-weighted images and high signal intensity on T2-weighted images (Fig 1). Pericardial cysts with proteinaceous content show high signal intensity with T1-weighted sequences and intermediate to low signal intensity with T2-weighted sequences. Diffusion-weighted imag-ing may be useful in these cases, as pericardial cysts do not demonstrate restricted diffusion and show high signal on apparent diffusion coefficient (ADC) maps (Fig 2) (16,17). Hemorrhagic cysts are hyperintense with T1-weighted sequences and demonstrate susceptibility with gradient recalled echo sequences. Surgical resection or percutane-ous drainage is reserved for symptomatic indi-viduals, when complications are present, or when the diagnosis is uncertain and pathologic analysis is needed (Fig 3) (15).


Figure 3. Acute inflammation in a chronically inflamed pericardial cyst. Contrast-enhanced CT im-ages (a obtained at a higher level than b) demonstrate a large, peripherally calcified, fluid-attenuation lesion along the left aspect of the pericardium that causes displacement of the left pulmonary artery. There is mass effect on the left atrium (arrows in b) and, to a lesser extent, on the left ventricle. Aspira-tion of the lesion yielded an exudate, and after surgical resection, pathologic analysis revealed acute on chronic inflammation of a pericardial cyst.

Figure 2. Proteinaceous pericardial cyst. (a) T1-weighted MR image demonstrates a high-signal-intensity well-defined lesion in the anterosuperior aspect of the pericardium. (b) T2-weighted MR image obtained at the same level shows intermediate to low signal intensity in the lesion. (c) ADC map reveals high signal intensity in the mass, a finding that confirms the cystic nature of the lesion. Findings on T1- and T2-weighted images are in keeping with proteinaceous content.

Pericardial LipomaPericardial lipomas are benign lesions that most commonly grow in an insidious fashion, therefore resulting in few symptoms (18). As with subcuta-

neous lipomas, pericardial lipomas are encapsu-lated; however, unlike their subcutaneous coun-terparts, lipomas in the pericardium tend to be less circumscribed: Their contours are determined by the space they occupy (Figs 4, 5). Symptoms, when present, are usually related to compression of adjacent structures (Fig 5).


Figures 4, 5. (4) Pericardial lipoma. Noncontrast CT image of the chest demonstrates a large, low-attenuation intrapericardial lesion that insinuates into the pericardial recesses and conforms to the pericardial space. (5) Large pericardial lipoma. Contrast-enhanced CT scan of the chest shows a large low-attenuation lesion confined to the pericardium that conforms to the pericardial space and its re-cesses. The mass demonstrates no enhancing components. There is associated mass effect on the right and left atria (arrows).

At echocardiography, pericardial lipomas ap-pear echogenic. CT findings are usually diagnos-tic, as these lesions demonstrate homogeneously low attenuation (


Figure 7. Pericardial lipoblastoma in a young boy. Coronal T1-weighted MR (a) and axial contrast-enhanced CT (b) images of the chest show a large, well-defined, fatty pericardial mass with scattered enhancing septa. The patient’s age at presentation favors a diagnosis of lipoblastoma over liposarcoma.

for superficial lesions that are well encapsulated. Deep lipoblastomas tend to be unencapsulated and diffuse, and they may demonstrate a more infiltrative behavior. When these features are present, the proper term is lipoblastomatosis (21,22). Occasionally, lipoblastomas may arise in the pericardium.

The imaging features of pericardial lipoblas-toma are similar to those of pericardial lipomas. These lesions appear as an echogenic mass at echocardiography. On CT images, they are pre-dominantly low in attenuation and may dem-onstrate septations of soft-tissue attenuation. At MR imaging, lipoblastomas follow subcutane-ous adipose tissue signal and therefore appear hyperintense with T1-weighted sequences and intermediately intense to hyperintense with T2-weighted sequences. The most characteristic feature is the presence of septations and intra-tumoral streaks that represent the fibrovascular network (Fig 7). Occasionally, cystic changes may be present (21,22).

Pericardial ParagangliomaIntrapericardial paragangliomas are slow-growing tumors derived from neural crest cells and most often are nonfunctioning (23,24). Their func-tioning counterpart is exceedingly rare (25). Although most paragangliomas are benign, a minority of these neoplasms may exhibit locally invasive behavior or distant metastatic disease

(24). As with paragangliomas in other anatomic locations, when intrapericardial paragangliomas are functioning, they result in symptoms related to elevated plasma levels of catecholamines, such as tremors, sweating, palpitations, headaches, and hypertension. Nonfunctioning intrapericardial paragangliomas are either incidentally discovered at imaging or are found as the culprit lesion when patients present with symptoms derived from compression of mediastinal structures. Intraperi-cardial paragangliomas most commonly arise ad-jacent to the left atrium or anterior to the aortic root near the origin of the coronary arteries.

On chest radiographs, an intrapericardial paraganglioma commonly resembles left atrial enlargement and is seen as a mass that splays the carina (23). CT and MR imaging are useful in further localizing and characterizing the lesion and play important roles in surgical planning. On contrast-enhanced CT images, the paragangli-oma appears as a hyperenhancing vascular mass (Fig 8). In approximately one-half of the patients, a central area of low attenuation that most likely represents necrosis or degeneration is seen (23). The characteristic MR imaging feature is hyper-intense signal with T2-weighted sequences. Con-trast-enhanced T1-weighted images demonstrate findings similar to those seen on CT images. Cross-sectional imaging is useful for assessing the relationship of the tumor to adjacent structures, in particular invasion of the adjacent atrium (23). Patients may undergo imaging with indium 111 pentreotide, 131I MIBG, or 123I MIBG scintig-


raphy as part of their work-up. Scintigraphy demonstrates an intrathoracic focus of increased tracer activity and is especially useful when the lesion remains occult with other imaging modali-ties (Fig 8) (5,23,26). 111In pentreotide is the nuclear medicine agent of choice, with a sensitiv-ity of 94%. The sensitivity of MIBG scintigraphy is lower, as it accumulates in only functioning paragangliomas (26). An intrathoracic focus of increased tracer activity is present in more than 90% of patients (Fig 8) (23). Conventional coro-nary angiography may also play an important role if surgery is planned. In some paragangliomas, the blood is supplied by vessels originating from the coronary arteries, and resection could result in myocardial ischemia unless appropriate presur-gical planning is conducted (24).

Germ Cell TumorsGerm cell tumors may arise from the pericar-dium. These tumors are composed of tissue from at least two of the three germ cell layers. The majority of germ cell tumors are located ante-

riorly and to the right. Most of them manifest in the newborn period or infancy. Diagnosis is increasingly made in utero at prenatal ultraso-nography. Mature teratomas are generally cystic and are typically attached by a fibrous pedicle to the heart or great vessels. When these lesions are detected in utero, the main finding is that of fetal hydrops (fetoplacental anasarca, pleural or pericardial effusion) (8). The presence of an asso-ciated pericardial effusion in neonates may result in a surgical emergency if tamponade physiology is found. When present in young adults, germ cell tumors are usually asymptomatic.

On CT images, germ cell tumors are usually well-defined, heterogeneous, multilocular masses. Typically, the cystic component predominates. Calcifications are common, and fat is seen in about 75% of patients. On MR images, teratomas are heterogeneous masses with signal intensity characteristics that correspond to those of their components (Fig 9) (5,8,27).

Figure 8. Paraganglioma. (a) Axial contrast-en-hanced CT image of the chest shows an enhancing mass (arrow) that arises from the posterior aspect of the pericardium, adjacent to the left atrium. (b) An-terior (left) and posterior (right) projections from an iodine 123 metaiodobenzylguanidine (MIBG) scintigraphic study demonstrate focal uptake in the mediastinal region, left of the midline, correspond-ing to the mass seen at CT, a finding that confirms this lesion to be a pericardial paraganglioma. (Case courtesy of Sanjeev Bhalla, MD, Mallinckrodt Insti-tute of Radiology, Washington University School of Medicine, St Louis, Mo.)


Pericardial HemangiomaPericardial hemangiomas can occur in any age group and are commonly found incidentally at autopsy. The histologic classification includes capillary, cavernous, or venous type. When aris-ing from the pericardium, hemangiomas are most often of the cavernous type and they usu-ally arise from the visceral pericardium (28,29). Their size ranges from 1 to 8 cm, and although most pericardial hemangiomas are solitary, cases of multiple lesions have been described (8). Oc-casionally, patients will present with hemoperi-cardium and findings of cardiac tamponade. It has been suggested that these conditions may develop from friction that ruptures neoplastic vessels (30,31).

As with hemangiomas that occur elsewhere in the body, pericardial hemangiomas appear as heterogeneous lesions on noncontrast-enhanced CT images and may contain foci of calcification. When contrast material is administered, they avidly enhance. At MR imaging, the hemangioma appears as a mass with intermediate T1-weighted signal intensity and high T2-weighted signal intensity. Upon contrast material administration, hemangiomas demonstrate nodular areas of en-hancement with progressive filling on delayed im-ages. Hemangiomas show benign features, such as well-circumscribed borders and no evidence of

invasion of neighboring structures (8,28,31,32). These features help differentiate these lesions from angiosarcoma.

Pericardial FibromaPericardial fibromas are benign tumors. They may grow to a large size and result in very minor symptoms. At CT, a fibroma appears as a soft-tissue attenuation mass. Fibromas are character-istically hypointense on T2-weighted MR images and isointense on T1-weighted MR images (33). On MR images obtained after the administration of gadolinium, fibromas demonstrate little en-hancement, and when enhancement occurs, it is often heterogeneous (16).

Inflammatory PseudotumorInflammatory pseudotumor is a benign process most commonly seen in the lung and orbit, but it can arise anywhere in the body, including the pericardium (34,35). The cause of inflammatory pseudotumor is unknown. Some cases develop secondary to surgery or trauma; some have been associated with IgG4-related sclerosing disease. Some authors argue in favor of a low-grade neo-plastic process. A subset of cases has been seen in association with an infectious agent such as Mycoplasma and Nocardia bacteria. Inflamma-tory pseudotumor is most often seen in children and young adults, but cases in older patients have been described as well (34,36).

Figure 9. Intrapericardial teratoma. (a) Fetal sonogram shows a large echogenic intrapericardial mass (straight arrow) adjacent to the heart and associated with a pericardial effusion (curved arrows). (b) Coronal T2-weighted fetal image shows the heterogeneous mass (straight arrow) adjacent to the heart (curved arrow) and associated with a pericardial effusion. (Fig 9a and 9b re-printed, with permission, from reference 27.)


Figure 10. Inflammatory pseudotumor in a 35-year-old man. (a, b) Short-axis balanced steady-state free precession (a) and sagittal black blood half-Fourier acquired single-shot turbo spin-echo (b) MR images show a homogeneous, intermediate- to low-signal-intensity pericardial mass sitting on the anterolateral wall of the left ventricle and encasing, but not obstructing, the left anterior descending artery (arrow). (c) Con-trast-enhanced short-axis volumetric interpolated breath-hold examination (VIBE) MR image demonstrates brisk and homogeneous enhancement (*). (d) Axial PET/CT image demonstrates high FDG uptake within the mass. Results of pathologic analysis demonstrated an idiopathic fibroinflammatory process.

At imaging studies, inflammatory pseudotu-mor mimics a neoplasm. On CT images, these lesions have a variable appearance. Typically, a mass of heterogeneous attenuation and en-hancement is seen (34). An associated pericar-dial effusion may be present (35). On T1- and T2-weighted MR images, inflammatory pseudo-tumor usually has low signal intensity due to the fibrotic nature of the lesion. After administration of gadolinium contrast material, these lesions may show homogeneous or heterogeneous en-

hancement. On PET/CT images, these lesions show increased FDG uptake (Fig 10) (34,36).

Primary Malignant Pericardial Mesothelioma

Primary malignant pericardial mesothelioma is extremely rare, with a reported prevalence of 0.0022% at autopsy series. It is, however, the most common primary malignancy of the pericardium (37,38). Pericardial mesothelioma occurs more


and similar to those of other pericardial ma-lignancies. Manifestations include constrictive pericarditis, pericardial effusion (Fig 11), tam-ponade physiology, and myocardial infiltration, which may result in conduction abnormalities (42). Pericardiocentesis commonly reveals hem-orrhagic fluid, with malignant cells seen in only 20% of the cases (37).

Figures 11, 12. (11) Primary pericardial mesothelioma in a 65-year-old woman. (a) PET/CT image demonstrates a pericardial mass with avid FDG uptake that encases the heart. (b) Contrast-enhanced CT image obtained at a later date demonstrates interval development of an associated large pericardial effusion. The solid component is less conspicuous at CT. (12) Pericardial mesothelioma. (a) Contrast-enhanced CT image demonstrates a heterogeneously enhancing mass that involves the pericardium and completely encases the heart. There is loss of the epicardial fat plane along most of the ventricular walls (arrow), a finding consistent with epicardial and possibly myocardial invasion. (b) Balanced steady-state free precession MR image obtained during diastole shows the heterogeneous mass confined to the pericar-dium and encasing the heart. Cine loop (not shown) demonstrated marked diastolic impairment.

frequently in men than women, manifesting most often in the 5th through 7th decades of life (39). Three variants exist— epithelial, biphasic (mixed), and fibrous (spindle cell)—with epi-thelial cell being the most common (40). Unlike pleural mesothelioma, which has a proved as-sociation with asbestos exposure, the association of pericardial mesothelioma with asbestos is still controversial (41). Length of survival is dismal, ranging between 6 weeks and 15 months, re-gardless of therapy (42). Symptoms are vague


The sensitivity of echocardiography in the detection of pericardial mesothelioma is low (8). CT and MR imaging offer an advantage, as these modalities better depict the extent of disease. On both CT and MR images, pericardial mesothe-lioma appears as a heterogeneously enhancing mass that involves both the parietal and visceral layers of the pericardium, with possible invasion of the adjacent vascular and anatomic structures (Figs 11, 12). MR imaging is helpful in providing information regarding the degree of constriction (42) and diastolic impairment (Fig 12). At FDG/PET, these neoplasms demonstrate hypermeta-bolic activity (Fig 11). Metastatic disease is found in approximately 50% of the cases, most com-monly in local mediastinal lymph nodes and the lungs (43).

Resection may be curative in cases of localized disease. Most often, these patients require a peri-cardiectomy for palliation purposes, as this proce-dure prevents cardiac tamponade and relieves symptoms from pericardial constriction. Radia-tion therapy and chemotherapy have a limited role in cases of nonresectable disease (39,42,44).

Primary Pericardial SarcomasPrimary pericardial sarcomas are uncommon neoplasms with a wide range of histologic appear-ances. Histopathologic classification is imperative for guiding therapy. Subtypes include angiosar-coma, synovial sarcoma, fibrosarcoma, liposar-coma, rhabdomyosarcoma, and undifferentiated sarcoma among others (45). The prognosis for patients with this group of neoplasms is uniformly poor, with a dismal length of survival ranging be-tween 3 and 12 months (45).

AngiosarcomaPericardial angiosarcomas are vascular, highly aggressive neoplasms that frequently manifest with associated hemopericardium (46–48). Echocardiography commonly demonstrates a pericardial effusion, but it may fail to show a mass, because the depiction depends on a good acoustic window (47,48). Pericardiocentesis will often yield bloody fluid that may not contain malignant cells (48).

CT reveals the vascular and aggressive nature of angiosarcomas. These lesions are usually lob-ulated, vegetated masses that heterogeneously enhance at CT with areas of necrosis (7,47). On T1-weighted MR images, the signal intensity of angiosarcoma is heterogeneous and variable, depending on the degree of hemorrhage and necrosis in the tumor; however, angiosarcoma is predominantly isointense relative to myocar-dium. On T2-weighted and steady-state free pre-cession images, these masses appear heteroge-neous and hyperintense relative to myocardium (Fig 13). Angiosarcoma is usually associated with the right atrioventricular groove, parasit-izing blood flow from the right coronary artery. Large vascular channels may be seen as intrale-sional flow voids (46,49). On contrast-enhanced images, angiosarcomas may show avid enhance-ment with a “sun ray” appearance (50). Both CT and MR imaging play an important role in depicting the degree of tumor invasion of adja-cent structures. MR imaging may demonstrate constrictive physiology with diffuse thickening of

Figure 13. Pericardial angiosarcoma arising about the right atrium in a 54-year-old man. (a) Coronal black blood half-Fourier acquired single-shot turbo spin-echo image demonstrates a heterogeneous le-sion with foci of increased intensity, findings consistent with areas of necrosis. (b) Contrast-enhanced horizontal long-axis balanced steady-state free precession image reveals compression and invasion of the right atrium.


Figure 14. Primary pericardial synovial sarcoma in a 30-year-old man who presented initially with pro-gressive dyspnea and lower-extremity edema. Axial (a) and coronal (b) contrast-enhanced CT images show a heterogeneously enhancing pericardial mass along the right atrium that causes significant compres-sion. Pathologic analysis revealed monophasic synovial sarcoma with chromosomal translocation. Initial transthoracic echocardiography (not shown) demonstrated a large pericardial effusion with tamponade physiology. At pericardiocentesis, 2 liters of hemorrhagic fluid was drained.

the pericardium (48). Pericardial angiosarcomas may prove challenging for the pathologist because the tissue obtained may be mistaken for mesothe-lioma or mesothelial hyperplasia (7). Prognosis is poor, with a survival time of 6–11 months (48).

Synovial SarcomaIn a recent review performed by Cheng et al (51), only 14 convincing cases of synovial sarcoma have been described in the English literature. The true prevalence of these neoplasms may be underestimated, however, perhaps because the tumors histologically may resemble mesothe-lioma (7,51). Similar to mesothelioma, synovial sarcoma may be a monophasic or biphasic tumor (51). However, unlike mesothelioma, synovial sarcoma usually manifests as a solitary mass and at an earlier age (median patient age at presenta-tion, 33 years) (51). Of note, 90% of patients have the reciprocal chromosomal translocation t(X;18) (p11.2; q11.2) (52,53). Often, at the pa-tient’s initial presentation, pericardial sarcomas are misdiagnosed as pericarditis, because pericar-diocentesis commonly reveals a hemorrhagic ef-fusion with no evidence of atypical cells (54,55).

At CT, synovial sarcomas appear as heteroge-neous soft-tissue attenuation masses. MR imag-ing demonstrates the high degree of vascular-ization of these neoplasms, and cross-sectional imaging in general is helpful for depicting their invasive nature. Synovial sarcomas may result in invasion of neighboring structures, infiltrat-ing the epicardium and myocardium, as well as encasing vessels (Fig 14). Metastatic involve-ment of mediastinal lymph nodes has also been described (Fig 15). Management includes a combination of surgery, radiation therapy, and chemotherapy (51).

FibrosarcomaOnly a few cases of pericardial fibrosarcoma have been described in the medical literature (56,57). As with other pericardial malignancies, fibrosarcomas often manifest with a large hem-orrhagic pericardial effusion. At CT, their imag-ing appearance is that of an infiltrative mass that may demonstrate central areas of necrosis. On T1- and T2-weighted MR images, they demon-strate heterogeneous signal intensity, reflecting some degree of necrosis and hemorrhage. Het-erogeneous enhancement can be seen after the administration of intravenous gadolinium (Fig 16) (57–59).


Figure 15. Primary pericardial synovial sarcoma. Fused PET/CT (a) and maximum intensity projec-tion PET (b) images, obtained in the same patient as in Figure 14 a few months later, show an interval increase in size of the mass. The mass has a central area of necrosis, as demonstrated by the peripheral rim of increased FDG uptake seen at PET/CT. Additional multiple foci of increased uptake are seen in the pericardium and mediastinum, findings consistent with locoregional spread of disease.

Figure 16. Primary pericardial fibrosarcoma in a 14-year-old girl. (a) Transthoracic echocardiogram demonstrates a large, predominantly echogenic, het-erogeneous pericardial mass along the free wall of the left ventricle (arrows). (b) Coronal black blood MR image reveals the large, centrally necrotic, in-trapericardial mass. (c) Coronal contrast-enhanced CT image shows the large mass along the left aspect of the pericardium. The low attenuation of the mass is in keeping with the extent of necrosis. Pathologic analysis revealed a pericardial fibrosarcoma. (Case courtesy of J. Delgado, MD, IATM, Medellin, Colombia.)


Figure 17. Primary pericardial rhabdomyosarcoma. Axial contrast-enhanced CT images of the chest obtained at the level of the pulmonary arteries (a) and heart (b) demonstrate a heterogeneous pericar-dial mass that encases the heart and great vessels. The mass invades the epicardial fat as well as the myo-cardium. Bilateral pleural effusions are also present.

LiposarcomaAbout a dozen cases of primary pericardial li-posarcoma have been described in the literature (60–63). These neoplasms are slow-growing tu-mors that are often large at presentation. Their large size and invasive nature limit complete surgical excision (61,63). Metastatic disease has been described (62,64). At imaging, pericardial liposarcomas appear similar to liposarcomas that occur elsewhere in the body. On CT images, pericardial liposarcomas appear as predominantly fatty to heterogeneous masses with areas of low-attenuation values. MR imaging also depicts their fatty nature and is useful for assessing the degree of invasion (61).

Rhabdomyosarcoma On rare occasions, a rhabdomyosarcoma may arise from the pericardium (65), and most of these cases have been observed in pediatric pa-tients (66). Rhabdomyosarcoma is a highly het-erogeneous tumor (65). On CT images, rhabdo-myosarcoma appears as a large, solid, infiltrative enhancing mass that can be homogeneous or het-erogeneous, depending on the degree of necrosis and cavitation (Fig 17) (10). Foci of calcification may be seen (66). At MR imaging, they appear predominantly isointense with T1-weighted sequences and hyperintense with T2-weighted sequences, with homogeneous to heterogeneous enhancement after the administration of gado-linium (10).

Undifferentiated SarcomaUndifferentiated sarcomas are malignant neo-plasms without specific histologic features (67). Patients usually present with symptoms related to a large pericardial effusion (67–69). On CT im-ages, an undifferentiated sarcoma may appear as a discrete, infiltrative enhancing mass, which can infiltrate the myocardium and invade adjacent vascular structures. On T1- and T2-weighted MR images, they usually appear isointense relative to myocardium and demonstrate a heterogeneous enhancement pattern (58). Treatment includes a combination of surgery, chemotherapy, and ra-diation therapy (67–69).

Pericardial LymphomaMost primary pericardial lymphomas are dif-fuse, large B-cell lymphomas (70). Pericardial lymphoma most frequently manifests as an ill-defined, infiltrative soft-tissue mass with an asso-ciated pericardial effusion.

On CT images, the soft-tissue component of pericardial lymphoma may appear iso- to hypoattenuating with heterogeneous enhance-ment (Fig 18). Pericardial lymphoma is hyper-metabolic at PET/CT (Fig 19). At MR imag-ing, it appears hypointense with T1-weighted sequences and iso- to hyperintense with T2-weighted sequences with variable heterogeneous enhancement. On occasion, a discrete mass is not seen, and the sole imaging finding may be diffuse pericardial thickening or effusion, which is commonly hemorrhagic (7,58,71,72). Hemor-rhagic pericardial effusion appears as hyperat-tenuation on CT images. On T1-weighted MR


images, hemorrhagic fluid demonstrates high signal intensity; it has intermediate signal inten-sity on T2-weighted images. Strands of fibrin and coagulated blood, with or without locula-

Figure 18. Primary pericardial lymphoma. Con-trast-enhanced CT image of the chest demonstrates a lobulated, heterogeneously enhancing soft-tissue mass, predominantly along the anterior aspect of the pericardium. Note the obliteration of the epicardial fat (arrow) in keeping with epicardial invasion.

Figure 19. Primary pericardial lymphoma. (a) Contrast-enhanced CT image demonstrates a homogeneously enhancing mass along the anterior aspect of the pericardium that extends into the right atrioventricular groove and encases the right coronary artery (arrow). (b) PET/CT image at the same level shows homogeneous FDG uptake throughout the mass. (c) PET/CT image obtained 1 year later, after chemotherapy, demonstrates complete resolution of the hyper-metabolic mass.

tions, can be seen on steady-state free precession images (73). In patients with human immuno-deficiency viral infection or acquired immuno-deficiency syndrome (AIDS), a large pericardial effusion should raise suspicion for primary effusion lymphoma. These are human herpes-virus-8–associated large B-cell lymphomas that account for approximately 4% of AIDS-related lymphomas (74).


Figure 20. Pericardial primitive neuroectodermal tumor in a young female patient. Axial (a) and coro-nal (b) contrast-enhanced CT images of the chest show an aggressive, heterogeneous mass that com-pletely encases the heart and great vessels. The mass extends into the right atrioventricular groove with right atrial invasion (arrow in a) and lifts the cardiac base off the diaphragm. (Case courtesy of Claudia Varon, MD, retired from University of Southern California.)

Primary Pericardial Primi- tive Neuroectodermal Tumor

Primary pericardial primitive neuroectodermal neoplasms arise from cells of the primitive neuro-ectoderm. The extraosseous variety characteristi-cally occurs in young adults (75). The majority of cases demonstrate the chromosomal translocation t(11;22)(q24;q12) (76). To our knowledge, until now, only three cases of primary cardiac primi-tive neuroectodermal tumors have been reported in the English literature, of which only one arose from the pericardium (75).

On CT images, primary pericardial primitive neuroectodermal tumors are heterogeneous in appearance with foci of necrosis. They generally demonstrate aggressive features, with invasion of the myocardium and extension into adjacent mediastinal and vascular structures (Fig 20). These tumors are generally iso- to hypointense on T1-weighted MR images, are intermediate to hyperintense on T2-weighted MR images, and demonstrate homogeneous to heterogeneous enhancement after the administration of intrave-nous gadolinium.

SummaryPrimary pericardial neoplasms are rare but rele-vant tumors, because even when they are benign, these neoplasms may result in significant cardio-

vascular complications because of their anatomic location. The most common benign lesion is a pericardial cyst. Patients with malignant pericar-dial neoplasms have a dismal prognosis, which is partially because they present at a late stage in their disease, often after invasion of vital medias-tinal or cardiac structures has occurred. The most common malignant primary pericardial neoplasm is mesothelioma.

The radiologist can play a key role in the care of patients with pericardial neoplasms. CT and MR imaging are fundamental in the evaluation of these neoplasms and may, in some occasions, allow full characterization of their features. Most important, the role of the radiologist centers in aiding the clinical team to guide therapy. Atten-tion should be directed at the location of these le-sions and the extent of disease, including invasion of adjacent structures, involvement of the coro-nary arteries, compression of cardiac chambers, pericardial effusion, constrictive physiology, and locoregional or distant metastatic disease.

Disclosures of Conflicts of Interest.—S.M.J.: Related financial activities: none. Other financial activities: royal-ties from Amirsys.

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This journal-based SA-CME activity has been approved for AMA PRA Category 1 CreditTM. See www.rsna.org/education/search/RG.

Teaching Points October Special Issue 2013

Primary Pericardial TumorsCarlos S. Restrepo, MD • Daniel Vargas, MD • Daniel Ocazionez, MD • Santiago Martínez-Jiménez, MD • Sonia L. Betancourt Cuellar, MD • Fernando R. Gutierrez, MD

RadioGraphics 2013; 33:1613–1630 • Published online 10.1148/rg.336135512 • Content Codes:

Page 1614Patients with primary pericardial neoplasms present with diverse symptoms. Clinical signs and symptoms are usually the result of associated pericardial effusion, pericarditis, or invasion of adjacent structures and are therefore nonspecific. Symptoms include exertional dyspnea, chest pain, cough, palpitations, fatigue, night sweats, fever, and facial or lower-extremity edema. Occasionally, a primary pericardial tumor may be found incidentally in an asymptomatic patient, during work-up for an unrelated illness.

Page 1614Some of the commonly seen complications include invasion of mediastinal structures, regional or dis-tant metastases, pericardial effusion, cardiac tamponade, compression of vascular structures or cardiac chambers, encasement of vital structures, involvement of coronary arteries, myocardial infarction, diastolic dysfunction, and constrictive physiology.

Page 1615Typically, pericardial cysts appear on CT images as well-defined, nonenhancing, homogeneous fluid-attenuation lesions that contain no internal septa. Occasionally, the cyst may contain proteinaceous fluid, in which case the lesion will demonstrate intermediate attenuation at CT. Pericardial cysts with hemorrhagic contents appear with hyperattenuation at CT. MR imaging offers further characterization of the internal contents of the cysts. Usually, pericardial cysts demonstrate intermediate to low signal intensity on T1-weighted images and high signal intensity on T2-weighted images.

Page 1617Lipomas appear as nonenhancing lesions that are hyperintense on T1-weighted MR images and interme-diate to high signal intensity on T2-weighted MR images. Use of fat-saturated sequences to confirm the fatty nature of the lesion is helpful, as these sequences will result in a uniform drop in signal.

Pages 1621Primary malignant pericardial mesothelioma is extremely rare, with a reported prevalence of 0.0022% at autopsy series. It is, however, the most common primary malignancy of the pericardium.

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Primary Pericardial Tumors · 1616 October Special Issue 2013 radiographics.rsna.org Figure 3. Acute inflammation in a chronically inflamed pericardial cyst. Contrast-enhanced CT