A 65-year-old female was admitted with progressive exertional dyspnoea and chest pain. Chest radiography revealed an enlarged cardiac silhouette suspicious for a large pericardial effusion (Fig. 1a). Transthoracic echocardiogram was normal, apart from a large echo-lucent space strictly limited to the anterolateral border of the left ventricle (Fig. 1b). Computed tomography scan showed a large cystic mass at the left heart border (17 × 7 cm, see Fig. 1c). Patient underwent video-assisted thoracic surgery in which the entire cyst was removed. During surgery the diagnosis pericardial cyst was confirmed. Chest radiography afterwards showed a normal heart contour (Fig. 1d).

Fig. 1
figure 1

a Chest radiography showing an enlarged cardiac silhouette, b TTE showing the presence of an echo-lucent space adjacent to the left ventricle, c CT heart image showing a lobulated, low-signal-intensity, cystic mass within the pericardium to the left of the left heart border, d Chest radiography showing a normal heart contour after surgical removal of the pericardial cyst (CT computed tomography, TTE transthoracic echocardiography)

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Pericardial cysts are mostly diagnosed in women around 50 years [1]. Ninety percent of the patients are asymptomatic. If symptoms occur, chest pain is most common, followed by dyspnoea and palpitations [1].

Pericardial cysts are located in the right heart border in 80%, less frequently in the left heart border (15%) and, rarely, in the anterior mediastinum [1].