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Key Points

  • Differential diagnosis includes bronchogenic cyst, pericardial cyst, thymic cyst, esophageal duplication, and neurenteric cysts.

  • Sonographic features may be used to differentiate between various cystic masses that may be found in the fetal chest.

  • MRI scanning is often a useful adjunctive imaging modality to ultrasound that may allow more accurate diagnosis and recognize mass effect on adjacent structures.

  • Fetal intervention may be indicated by thoracoamniotic shunting for hydrops.

  • EXIT-to-ECMO or EXIT-to-Resection may be indicated in cases in which the cystic lesion is very large and the airway is compromised.


Cystic lesions of the fetal chest include a broad list of anomalies that differ in origin, prenatal natural history, pathophysiology, and implications for management of the fetus. The most common lesions of the fetal chest include congenital pulmonary airway malformation (CPAM) (see Chapter 35) and bronchopulmonary sequestration (BPS) (see Chapter 34). This chapter focuses on other less common causes of fetal thoracic cysts including bronchogenic cysts, congenital lobar emphysema, pericardial cyst, thymic cyst, esophageal duplication cysts, and neurenteric cysts.

Bronchogenic cysts result from premature foregut remnants that originate in embryonic bud tissue prior to the formation of the bronchi. While bronchogenic cysts can share common features with esophageal duplication cysts, they are histologically characterized by the presence of cartilage, smooth muscle, and glands in the cyst wall (McAdams et al., 2000; Stocker, 2002; Langston, 2003). Most bronchogenic cysts occur in the mediastinum adjacent to the distal trachea or mainstem bronchi (McAdams et al., 2000; Stocker, 2002). Bronchogenic cysts can also be found within the lung parenchyma (McAdams et al., 2000; Langston, 2003). However, this is a controversial point, as some have considered these lesions a form of type I CPAM (Stocker, 2002). Bronchogenic cysts are unilocular and do not communicate with the tracheobronchial tree and are usually filled with mucus. Bronchogenic cysts can enlarge to produce airway compression and may ulcerate the cyst wall lining due to ectopic gastric mucosa (Eber, 2007). Histologically, bronchogenic cysts are lined with ciliated columnar epithelium and contain bronchial mucous glands, elastic tissue, and hyaline cartilage (Maier, 1948) (Figure 36-1).

Figure 36-1

A T1-weighted fetal MRI attained at 28 weeks’ gestation demonstrating lobar emphysema of the LUL that was due to a bronchogenic cyst compressing the left mainstem bronchus and the take off of the left upper lobe bronchus. The bronchogenic cyst could not be detected prenatally as the cyst fluid was of the same signal intensity as that of adjacent mediastinal tissues.

Congenital lobar emphysema is characterized by over-inflation, either by retained fluid produced in the lobe or segment prenatally or by air trapped in the lobe or segment postnatally (Clements, 1999). Congenital lobar ...

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