Case presentation

A 29-day-old female neonate was referred to King Abdulaziz Cardiac Center (KACC) because of respiratory distress. She was a product of a caesarean section after a full-term uneventful pregnancy in Hail General Hospital. Her mother was healthy with one previous termination of pregnancy and no living children. She developed severe respiratory distress immediately after birth, required intubation and ventilation, and received two doses of synthetic surfactant. She was extubated at 11 days of age and then transferred to the general ward. Her septic workup was negative. However, she remained in respiratory distress needing supplemental oxygen, so a transthoracic echocardiogram was performed and showed a huge cystic mass compressing the surrounding structures. Subsequently, she was referred to our cardiac centre.

On arrival to our Pediatric Cardiology Ward, her weight was 2.9 kg, pulse 146 per minute, and respiratory rate 48 per minute. She was in notable distress with tachypnoea, intermittent flaring, and grunting. However, no stridor or wheezing was noted. She was maintaining normal oxygen saturation on minimal oxygen by nasal cannula. Her chest radiograph did not show a major abnormality. Her echocardiogram (Fig 1) showed a large cystic chest mass originating posteriorly and exerting compression effects on the left atrium and pulmonary artery branches. The right pulmonary artery was severely compressed with diminished flow and high peak gradient, while the left was less affected. The mass appeared to have no clear communication with the heart, which was confirmed by CT imaging (Fig 2). For a rotational movie of rendered 3-d images, please refer to the data supplement (Movie 1).

Figure 1. Transthoracic echocardiographic images. Transthoracic echocardiographic views showing a huge mass posterior and superior to the heart with compression of the left atrium, as seen from subcostal (a), high parasternal (b), and suprasternal views (c). The Color Flow Doppler (b, on the right) demonstrates branch pulmonary arteries compression. The mass was extending superiorly underneath the aortic arch (c). No communication of flow with the mass was noted on Color Doppler Flow (b, c).

Figure 2. CT images. CT angiographic coronal (a), axial (b) sagittal, (c), and 3D (d) views demonstrating a huge extra-cardiac nonenhanced homogeneous mass, with fluid content based on the Hounsfield unit. The mass measures 21 × 23 mm and is located in the superior–posterior aspect of the left atrium, compressing the airway and pulmonary artery branches, and shifting the aortic arch towards the left side. No communication was seen between the heart structures and this mass. It appears as a space-occupying lesion in the maximum intensity projection and 3D views.

The patient underwent surgery on the 25 June, 2020. The surgery was performed by a cardiac surgeon and a paediatric surgeon together with standby cardiopulmonary bypass, via a median sternotomy. A large cystic mass was found superior to the left atrium (Fig 3a). It originated from the trachea just proximal to the bifurcation. It was tense and compressing the surrounding structures including the aorta and pulmonary arteries. The mass was mobilised free from all surrounding structures and resected off the trachea with no tracheal extension. The cyst was full of a clear serous fluid which leaked during excision, and the mass was sent for histopathological evaluation after resection. Intraoperative transoesophageal echocardiography showed no significant residual lesion.

Figure 3. Gross anatomy and histopathology. (a) Gross appearance of the surgically excised cystic mass, measuring around 18 × 8 mm. (b) Histological section showing the cyst wall with a lining of respiratory epithelium*, bronchial glands**, and cartilage*** (H&E stain). Bar = 0.300 mm.

The histopathological examination (Fig 3b) showed the cyst to be unilocular and lined by ciliated pseudostratified columnar epithelium of respiratory type. The wall contained hyaline cartilage, smooth muscle, bronchial glands, brown fat, and nerve fibres. Those findings were consistent with a diagnosis of a bronchogenic cyst.

After surgery, she was transferred to the Pediatric Cardiac Intensive Care Unit (PCICU) and successfully extubated within 24 hours. She developed left lung atelectasis that was found to be related to left diaphragmatic paresis confirmed by ultrasound examination. Most probably this was due to left phrenic nerve paresis which was close to the lesion during dissection. She had transient hypertension which was controlled by medication. Feeding was established and well tolerated. She stayed 10 days in the Paediatric Cardiac Intensive Care Unit after which she was transferred to the Stepdown Unit in a stable condition. Oxygen was weaned off gradually and feeding was optimised. She was discharged home in a healthy condition after 20 days of total hospital stay. At the follow-up visit, the infant was asymptomatic and had no residual lesion on echocardiography.