Corresponding Author
Key words: cancer, cardiac magnetic resonance, computed tomography, postoperative, treatment
Pericardial cysts are rare and generally benign lesions with an estimated incidence of about 1 in 100,000 individuals.1,2 Most are congenital malformations, where the mesenchymal lacunae that eventually form the pericardial sac have failed to fuse.2,3 Acquired forms of pericardial cysts include those associated with infection, pericarditis, systemic inflammation, or cardiac surgeries or procedures.3, 4, 5 Pericardial cysts most commonly arise at the right cardiophrenic angle (up to 70%) followed by the left cardiophrenic angle, and rarely, elsewhere in the mediastinum.4 Pericardial cysts are typically <5 cm in diameter, however larger cysts have been reported.2,4 In a single-center study that included 29 asymptomatic patients with pericardial cysts who had repeat imaging, 48% had no significant change in size, 34% had a decrease, and 17% had an increase in size by 0.6 cm.6 Over 50% of individuals with pericardial cysts remain clinically silent and can be observed with serial imaging.2,5 Those who develop symptoms from compression may require treatment with percutaneous aspiration or surgical excision.5
In this issue of JACC: Case Reports, Naoun and Pandey7 present an interesting and educational case of a pericardial cyst that can mimic a more sinister etiology. In their 52-year-old female patient who underwent bilateral mastectomy because of recurrent breast cancer, a pericardial cyst measuring 5.0 × 1.3 cm was incidentally found when planning for a delayed breast reconstruction surgery. During postoperative hospitalization, the pericardial cyst was noted to have grown in size to 5.8 × 2.1 cm, but it then regressed to 4.9 × 1.2 cm the month after. In the context of recent recurrent breast cancer, these findings were concerning for malignant involvement of the pericardium. However, benign features on computed tomography (CT) and magnetic resonance imaging (MRI), as well as the transient nature of the enlargement occurring shortly after surgery and subsequently regressing, is more suggestive of a reactive inflammatory response rather than malignant infiltration. Postsurgical inflammation likely caused transient fluid accumulation within the cyst, driven by increased capillary permeability and local tissue reaction near the surgical field.
This case highlights the importance of using imaging features to help differentiate a more benign etiology from a malignant one for pericardial masses. On a transthoracic echocardiogram, a pericardial cyst appears as a well-circumscribed, anechoic space that is most commonly located next to the right atrium.1,5 Lack of blood flow in the structure as demonstrated with color Doppler supports the diagnosis of pericardial cyst as opposed to other vascular structures.1 The lack of ultrasound-enhancing agents, if used, within the cyst can further demonstrate the avascular nature and thus support the diagnosis of a pericardial cyst.5
While echocardiogram is frequently the first line test to detect pericardial cyst, CT or MRI offer superior tissue characterization as well as evaluation of invasion into the surrounding structures.5 On CT, pericardial cyst appears as a well-circumscribed, thin-walled unilocular fluid collection with attenuation of 0 to 20 Hounsfield units.5 If intravenous contrast is used, a pericardial cyst is nonenhancing given its avascular nature.5 On MRI, a pericardial cyst again appears as a well-defined, smooth-bordered lesion that demonstrates characteristics of simple fluid, such as a uniform low signal on T1-weighted images and a high signal on T2-weighted images.1,5 If gadolinium-based contrast is used, a pericardial cyst is nonenhancing, similar to contrast findings on CT or echocardiogram.1
In contrast to pericardial cysts, pericardial tumors (either primary or metastatic) are seen as echodense masses on the pericardium and may be nodular.5 These masses can be associated with pericardial thickening and pericardial effusion.5 CT and MRI again offer additional tissue characterization when pericardial tumor is suspected. The CT features of pericardial malignancy include irregular, thickened, nodular pericardium, disruption of the pericardial sac, invasion into the surrounding structures, and a complex pericardial effusion.5,8 Benign tumors, such as lipomas and teratomas, can be differentiated from malignant tumors by the presence of fat or fat with calcium, respectively.5 On MRI, malignant pericardial tumors have signal intensity characteristics similar to the myocardium on T1-weighted imaging and usually enhance with contrast because of the vascularity.5,8 Pericardial irregularity or effusions may support a malignant etiology, whereas well-defined or encapsulated lesions support a benign etiology.5
This case elegantly illustrates the imaging features that support a benign etiology despite the interval change in size. Combined with the asymptomatic nature of the patient, conservative management would be recommended.
Funding Support and Author Disclosures
The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
Footnotes
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References
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