Pericardial cyst

Clinical History

A 40-year-old male non-smoker came to the pulmonary outpatient department for check-up of lung functions due to occasional problems with breathing and suspicion of asthma. During diagnostic workup a routine chest radiograph showed a round-oval mass obscuring the right cardiophrenic angle.

Imaging Findings

Chest Radiograph shows a round/ oval mass that obscured the right cardiophrenic angle measuring approximately 5.5 cm in diameter (Figure 1).

Contrast enhanced CT of the thorax revealed a thin-walled, sharply defined, oval, homogeneous mass with attenuation near that of water measuring approx 7 x 7 cm in diameter in the right cardiophrenic angle, in the anterior mediastinum (Figure 2-5).

Discussion

BACKGROUND:

Pericardial cysts are benign lesions accounting for 5%–10% of mediastinal tumours. They are located more frequently in the right cardiophrenic space (77%) than the left (22%) [1, 2].

Pericardial cysts generally have a congenital origin and are due to a defect in pericardial development. These cysts are almost always asymptomatic and are detected as an incidental finding on routine plain radiographs [3].

Histologically, these cysts are lined with a single layer of mesothelial cells in a stroma of connective tissue. They contain a clear, water-like fluid, giving rise to the term “spring water cysts.” They vary from 2-15 cm in dimension and are commonly located in the anterior mediastinum at the cardiophrenic angle [4].

IMAGING PERSPECTIVE:

Chest Radiographs: A mass with well-defined borders occupying the cardiophrenic space is suggestive of pericardial/pleuropericardial cyst [3].

CT Examination: The characteristic CT appearance is a fluid-filled lesion with well-defined borders and smooth walls. Because of its fluid content, the cyst has a characteristic attenuation coefficient of 0–20 HU, although in sporadic cases the attenuation can be greater (30 HU) [3].

MR: MRI findings are diagnostic, the fluid content being reflected in pronounced homogeneous high signal intensity on T2-weighted images and low signal intensity on T1-weighted images. The lesions do not show significant enhancement after intravenous contrast material administration [3].

DIFFERENTIAL DIAGNOSIS:

1. Bronchogenic cyst - Single, smooth, round/elliptic mass with imperceptible wall and uniform attenuation (dependening upon the contents of the cyst and can vary from water attenuation to soft-tissue attenuation. The value can be more than 100 HU owing to high protein level or calcium oxalate in mucoid cyst) [5].

2. Hydatid cyst - Calcification of the cyst wall or internal septa is easily detected at CT.

3. Thymic cyst - On CT simple congenital, uni-/multilocular, thymic cysts usually appear as well-defined water-attenuation masses with imperceptible walls.

4. Mature cystic teratoma - On CT these tumours are heterogeneous, well-defined masses with walls of variable thickness that may enhance. They may contain all four tissue types, including soft tissue, fluid, fat, and calcium, but fluid-containing cystic components are usually prominent [5].

5. Lymphangioma - CT shows smooth, lobulated mass, which may mold to or envelop, rather than displace adjacent mediastinal structures. Unilateral/bilateral chylous pleural effusions may be present [5].

6. Many tumours can undergo cystic degeneration and demonstrate mixed solid and cystic elements at CT or MR imaging. If degeneration is extensive, CT and gross appearances of the lesion are indistinguishable from congenital cyst [5].

Differential Diagnosis List

Final Diagnosis

Right-sided pleuropericardial cyst.

URL:	https://www.eurorad.org/case/10439
DOI:	10.1594/EURORAD/CASE.10439
ISSN:	1563-4086