Pericardial cyst

Article written and reviewed by Dr Luca Moretti

A pericardial cyst is a generally benign, thin-walled, mesothelial-lined cavity containing fluid and located in relation to the pericardium. In its typical form, it does not communicate with the pericardial space: this feature distinguishes it from a pericardial diverticulum, although separation may be difficult with imaging alone.

Most cysts are discovered incidentally during thoracic investigations. The clinical issue is to recognize a simple lesion, distinguish it from lesions of another origin, and determine whether it causes compression or plausibly related symptoms. Size and the presence of symptoms alone are not sufficient to establish a surgical indication.

Echocardiography assesses the effect on the heart, whereas computed tomography and magnetic resonance imaging define contents, wall, and anatomical relationships. Management includes observation, aspiration in selected cases, and resection. The choice should consider the reliability of the diagnosis and the limitations of the evidence, which consists mainly of retrospective cohorts, surgical series, and descriptions of rare complications.

Origin, pathology, and distribution

Classic pericardial cysts arise from abnormalities in the organization of coelomic cavities during development. Small mesothelial spaces may persist as separate cavities or lose an original communication with the sac. This model explains the conceptual proximity between cyst and diverticulum but does not allow the embryogenesis of an individual lesion observed in an adult to be reconstructed with certainty. Late discovery is compatible with congenital origin and does not demonstrate that the lesion appeared recently.

The wall usually consists of fibrocollagenous connective tissue lined internally by flattened or cuboidal mesothelial cells. The contents are often clear, without solid components; the historical description of a "spring-water cyst" refers to this appearance but is not a diagnostic criterion. Inflammation, bleeding, or a higher protein concentration can alter its color and radiologic properties. Pathologic examination, when available, should document the type of lining and exclude cystic lesions of another nature.

The most characteristic location is the cardiophrenic angle, especially on the right, but left-sided and atypical locations along other pericardial segments are possible. Location influences both the likelihood of recognition and the differential diagnosis: a superior lesion may be mistaken for a thymic lesion or a distended recess, whereas a posterior lesion may raise the possibility of a bronchogenic or enteric duplication cyst. A typical location supports the hypothesis, but its absence does not exclude a mesothelial cyst.

Size ranges from small findings to large cavities that deform the cardiac silhouette. A regular unilocular morphology is typical without being obligatory in every presentation. Septa, a thickened wall, or nodules require an explanation and should not be normalized simply because the lesion touches the pericardium. Extension into the mediastinum and relationships with the atria, ventricles, coronary arteries, diaphragm, and phrenic nerve are more useful than maximum size alone for treatment planning.

There are also acquired lesions or pseudocysts associated with procedures, inflammation, or organized collections. These are not automatically equivalent to a simple congenital cyst and may not have the same lining. The history should therefore reconstruct thoracic surgery, trauma, infections, and previous pericardial disease. An organized hematoma may acquire a circumscribed appearance, whereas a loculated effusion may mimic an independent cavity; distinction derives from the combination of history, topography, and characterization of the contents.

Epidemiology is poorly defined because many cases remain silent and series come from imaging or surgical centers. Traditional estimates of rarity should not be interpreted as precise contemporary measures of incidence. Increasing use of thoracic imaging makes incidental detection more frequent without implying a biological increase in disease. There are no sufficiently documented common acquired risk factors that predict the development of a congenital cyst or justify screening in the general population.

Pathophysiology, symptoms, and clinical assessment

A simple cyst mainly exerts a possible mass effect. It does not necessarily alter cardiac function and is not, by definition, pericarditis. Symptoms depend on the direction of growth and compliance of surrounding structures: a relatively large cavity may be well tolerated if it occupies free space, whereas a smaller one may be significant if it compresses a vessel or chamber. The anatomical finding therefore needs to be linked to a demonstrable functional mechanism.

Dyspnea, persistent cough, and a feeling of chest heaviness are symptoms described in symptomatic cases. Airway compression may contribute to cough or recurrent respiratory infections; impaired right-sided filling may produce congestion. These mechanisms should not be inferred from proximity alone: relevant deformation and, when possible, altered flows should be demonstrated. Common alternative pulmonary and cardiac causes should be considered within the same diagnostic pathway.

Chest pain may be nonspecific, related to local tension or irritation, or caused by another condition. Acute pain with fever or rapid worsening requires evaluation for inflammation, infection, hemorrhage, or rupture, in addition to relevant coronary and aortic emergencies. A pre-existing diagnosis of a cyst does not justify automatically attributing every new episode to that finding. A patient can simultaneously have a stable benign lesion and an entirely independent urgent disease.

Palpitations and arrhythmias have been reported in association with cysts, but the causal link is often difficult to demonstrate. Electrocardiographic evaluation and, when appropriate, ambulatory monitoring should characterize the rhythm and its relationship to symptoms. It is not correct to assume that excision will eliminate an arrhythmia without a plausible anatomical or temporal correlation. Actual atrial compression provides a stronger pathophysiologic hypothesis than the mere coincidence of a radiologic finding and a rhythm complaint.

The physical examination is often normal. In more significant cases it may identify respiratory abnormalities, congestion, or low output, but there is no specific finding capable of identifying the cyst. The history should assess symptom course, relation to exertion and posture, oncologic history, and procedures. Previous images, including those obtained for noncardiac reasons, should be reviewed: long-term stability reduces the likelihood of an aggressive explanation but does not eliminate a possible compressive effect.

Functional assessment should answer a specific question. Echocardiography and Doppler can evaluate filling and flows; respiratory testing or rhythm monitoring is requested when consistent with symptoms. There is no need to construct an extensive panel for every small asymptomatic finding. When symptoms are disproportionate to the lesion, investigation of alternatives helps avoid unhelpful interventions. The final decision integrates severity, causal plausibility, and the possibility of benefit, not simply the desire to remove an abnormal image.

Diagnosis by echocardiography, CT, and MRI

On echocardiography, a typical cyst appears as a well-defined structure with anechoic contents adjacent to the heart. The examination should establish whether it is separable from the chambers and whether it causes compression, using Doppler to look for any flow suggesting a vascular structure. Visualization may be incomplete in superior or posterior locations and in patients with unfavorable acoustic windows. Echocardiographic follow-up is adequate only when the lesion can be recognized and measured reproducibly.

Chest radiography may show a smooth opacity along the cardiac border, often at the cardiophrenic angle, but it cannot reliably define its contents. Comparison with previous studies helps identify stability and change, taking projection and rotation into account. The finding may mimic cardiomegaly or a mediastinal mass and requires characterization if not already known. A normal radiograph does not exclude small lesions or those hidden by the cardiac silhouette and does not replace the imaging needed in symptomatic patients.

CT documents margins, density, any septa, and relationships with thoracic structures. Simple fluid has attenuation close to water and shows no internal enhancement. Higher density may result from protein or blood without proving solidity; conversely, an enhancing component requires evaluation. The radiologist should identify the plane of origin and any tract communicating with the pericardium, distinguishing a cyst from a diverticulum or recess.

On MRI, simple fluid is generally hypointense on T1 and hyperintense on T2, without enhancement of the contents. Multiple sequences and fat suppression help resolve cases that are atypical on CT; proteinaceous or hemorrhagic material can alter signal and requires integrated interpretation. Cine sequences show dynamic relationships with the heart, while characterization of the wall helps assess inflammation or suspicious components. MRI is particularly useful when serial comparisons are planned without radiation exposure.

Communication with the pericardium is the key discriminating feature from a diverticulum, but a thin neck may escape even careful imaging. Marked changes in shape or volume and continuity with a recess suggest a communicating cavity. It is useful to review all available acquisitions rather than judging a single section. Failure to visualize a tract should be stated as a limitation of observation, not as absolute proof of closure, particularly if other findings suggest dynamic behavior.

The final report should describe location, comparable dimensions, contents, wall, enhancement, anatomical relationships, and functional consequences, stating the degree of certainty. A generic label of pericardial mass leaves important decisions unresolved. PET, invasive angiography, or other modalities are not required for a characteristic simple cyst; they become relevant only for additional questions, such as suspected malignancy or unclear vascular relationships. The next test should fill a specific information gap rather than repeat information that is already sufficient.

Differential diagnosis and further investigations

A diverticulum is the main comparator because it may share location and fluid contents. Its continuity with the cavity permits fluid shifts that change the apparent volume. A lesion that markedly decreases or disappears between two studies should therefore prompt a search for a communication, without excluding other explanations. The implications are practical: aspiration or instillation of substances into a communicating cavity can involve the sac and should not be planned as if the lesion were certainly an isolated cyst.

A loculated effusion often follows the contours of surfaces and may occur after surgery or inflammation. Adhesions and atypical distribution can make it very similar to a cyst. An organized hematoma may add a wall, septa, and heterogeneous contents, especially after trauma or procedures. Chronology and signal changes help distinguish them, but some lesions remain indeterminate. The assessment should consider the possibility of an acquired collection before attributing the finding to a congenital anomaly.

Mediastinal cysts include bronchogenic, thymic, and enteric duplication cysts. Their location relative to the trachea, bronchi, esophagus, and thymus, together with content behavior and wall characteristics, guide diagnosis. Epithelial lining or the presence of cartilaginous and muscular elements may clarify the diagnosis histologically after excision. Proximity to the heart is not enough to define a lesion as pericardial. In particular, a protein-rich posterior cavity can mimic a solid mass if studied with only one sequence.

Neoplastic lesions with cystic degeneration require attention to nodules, irregular walls, enhancement, and infiltration. A known malignancy changes the level of suspicion but does not turn every regular cavity into a metastasis. Characterization may be supplemented by staging and sampling when the result changes treatment; in some cases, a safer extracardiac target is available. A positive PET scan alone does not prove malignancy, because inflammatory processes can also show uptake, whereas simple fluid contents may be metabolically uninformative.

Before puncture, vascular structures such as aneurysms, pseudoaneurysms, or venous dilatations must be excluded. Doppler and contrast imaging are interpreted together because slow flow or thrombosis may obscure the vascular nature. Suspected parasitic cysts also require a specific pathway based on epidemiology and imaging, avoiding unplanned aspiration. Differential diagnosis is not a theoretical list: it serves to prevent a dangerous procedure on a lesion that is not a mesothelial cyst.

Laboratory tests are guided by the findings: inflammatory markers and cultures when infection is suspected, hematologic or oncologic assessment when relevant, and preprocedural testing when an intervention is planned. There is no specific blood marker for a pericardial cyst. If the lesion is resected, the specimen should be sent for pathology; the gross appearance of clear fluid does not replace diagnosis. The decision to obtain tissue weighs uncertainty, symptoms, accessibility, and risk together, avoiding biopsies that would not change management.

Observation, aspiration, and surgical treatment

An asymptomatic, typical cyst without compression can be observed. Conservative management is supported by the often stable course in available cohorts, but it requires reliable initial characterization. There is no universally validated size threshold that mandates surgery in every patient. Size, critical location, true growth, and difficulty of follow-up should be integrated; a very large lesion deserves specific discussion even when reported symptoms are mild or absent.

Follow-up over time is individualized according to diagnostic certainty and behavior. Echocardiography is useful if the cyst is well visualized; otherwise, targeted MRI or CT may provide more reliable comparisons. Frequency should not be derived from a single rule: closer follow-up is more reasonable for uncertain or changing findings, whereas prolonged stability may allow longer intervals. Radiation, contrast, costs, and the likelihood that the test will change management are part of the assessment.

Percutaneous aspiration can reduce compression or provide an option for selected patients, particularly when surgical risk is high and access is favorable. It requires imaging guidance and confirmation of a nonvascular nature. The wall remains in place and may allow reaccumulation: immediate reduction therefore does not equal definitive cure. The fluid can be analyzed, but negative cytology does not fully characterize a suspicious wall or replace histology when that is necessary.

Sclerotherapy has been described in limited experiences but lacks robust comparative evidence and a universally accepted protocol. Any use requires expertise, careful selection, and reasonable exclusion of communication with the pericardial space to avoid chemical injury to the sac. It should not be presented as a routine procedure applicable to every cyst. When the diagnosis remains uncertain or solid components are present, simple aspiration with a sclerosant may be inappropriate compared with a strategy that permits complete tissue characterization.

Surgical resection is considered when there are attributable symptoms, compression, significant growth, complications, or unresolved diagnostic uncertainty. Thoracoscopy is often feasible, whereas open approaches may be required for adhesions, complex location, or critical relationships. The goal is to remove the lesion while protecting the phrenic nerve, heart, and vessels. Favorable surgical series do not demonstrate that all incidental findings should be operated on: treated patients are selected and do not represent the natural history of uncomplicated cysts.

Perioperative planning considers respiratory reserve, position, compression, and ability to tolerate the required ventilation. Intraoperative decompression may facilitate removal in selected cases, but the technique should respect the diagnostic suspicion and avoid contamination. After surgery, hemostasis, diaphragmatic function, and residual collections are assessed, and symptoms are compared with those before treatment. Anti-inflammatory drugs or antibiotics are not treatments for the simple cyst itself; they are used only for appropriate perioperative indications or associated disorders.

Complications, prognosis, and surveillance after treatment

The prognosis of a simple cyst is generally favorable. In the cohort of 103 patients described by Alkharabsheh and colleagues, most were asymptomatic; among 29 asymptomatic subjects with repeated comparable imaging, some cysts decreased in size, others remained stable, and a minority increased modestly. Mean follow-up was about two years. These data support proportionate management but do not define lifetime risk or the risk of atypical or complicated lesions.

Compression may involve cardiac chambers, veins, or bronchi and should be recognized on the basis of functional effects. Hemorrhage, infection, and rupture are described mainly in reports and selected series; their rarity prevents precise individual estimates. Rupture into the pericardial space may exceptionally be associated with tamponade. Presenting these possibilities as the likely evolution of every incidental cyst would be incorrect and could encourage invasive treatment not justified by the risk-benefit balance.

A sudden change in the clinical picture, with severe pain, fever, dyspnea, or instability, requires urgent assessment. In addition to cyst complications, common and potentially lethal cardiovascular and respiratory diseases must be excluded. Drainage of a compressive collection addresses the emergency, whereas definitive management depends on the cause and the residual wall. If infection is present, source control and antimicrobial treatment should be coordinated; simply evacuating a contaminated cavity may not be sufficient.

Recurrence is more plausible after aspiration than after complete excision because the cavity remains available for refilling. However, there is no single percentage applicable to all techniques and follow-up periods. After surgery, residual margins, the actual diagnosis, and anatomy determine surveillance. Reappearance of a lesion at the same site should be verified by direct comparison of images, distinguishing it from postoperative effusion, seroma, or another transient collection.

Treatment complications include bleeding, infection, nerve injury, pleuropulmonary problems, and persistent pain. Choice of approach and center experience help reduce these risks without eliminating them. Follow-up also assesses functional recovery: if the symptom that prompted intervention persists, concomitant causes should be investigated rather than immediately assuming recurrence. Availability of the histology report can close the diagnostic question or guide further evaluation when unexpected features emerge.

Long-term surveillance should be justified and understandable. A patient managed conservatively should know the warning signs for earlier reassessment and the purpose of follow-up; after complete resection of a benign lesion, repeated CT scans indefinitely are not automatically necessary. Physical activity and restrictions depend on symptoms, compression, and associated heart disease. Documenting size, location, diagnostic certainty, and the shared decision prevents every subsequent thoracic study from unnecessarily reopening an already resolved pathway while still allowing genuine changes to be recognized.

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