Intralobar pulmonary sequestration expanding toward the contralateral thorax: two case reports

BACKGROUND Intralobar pulmonary sequestration (ILS) is defined as a portion of parenchyma that is contained within the normal pleural investment of the lung but not connected to the tracheobronchial tree, and supplied by anomalous systemic arteries. As ILS is enveloped within the lobe of the normal lung, it is extremely rare for ILS to invade into the mediastinum. We report two atypical cases of infants with ILS expanded toward the posterior mediastinum and contralateral thorax through the pulmonary ligament. CASE PRESENTATION The first case involved a baby boy diagnosed at 30 weeks gestation with a cystic area in his right lower lobe. A chest computed tomography (CT) scan at 29 days of life showed low-density masses in the right lower lung and posterior mediastinum. A complete thoracoscopic right lower lobectomy was performed at 19 months of age. After ligation of the aberrant systemic artery, the mediastinal mass was pulled into the right pleural cavity. The mass was observed to connect to the right lower lobe mass as a segment of lung parenchyma situated within the normal pleural investment of the lung, and the patient was diagnosed with ILS. The second case involved the detection by chest CT of a left lower lung cystic mass that protruded into the posterior mediastinum and contralateral chest of a one-month-old baby girl. A complete thoracoscopic left lower lobectomy was performed at the age of 18 months, and the cystic mass located in the right thoracic cavity was pulled easily into the left pleural cavity and resected. An anomalous systemic artery was identified and ligated, and the patient was also diagnosed with ILS. CONCLUSIONS As the pulmonary ligament consists of two layers of mediastinal pleura, lower lung ILS with its visceral pleura covering can, though rarely, protrude into the mediastinum through the pulmonary ligament. Our two extremely rare cases of infants with ILS expanded toward the posterior mediastinum and contralateral thorax were successfully treated using a unilateral thoracoscopic approach. Pre-surgical differential diagnosis of mediastinal masses using contrast-enhanced multiple detector CT is important in informing the appropriate surgical approach.