From the archives of the AFIP. Extralobar sequestration: radiologic-pathologic correlation.

Extralobar sequestration is a rare congenital anomaly that consists of pulmonary tissue anatomically separate from normal lung and usually deriving its blood supply from systemic vessels. The lesion typically manifests in the newborn period or early infancy with symptoms of respiratory distress. Less frequently, patients present in childhood or adulthood. Grossly and microscopically, the lesion resembles lung tissue. The typical radiologic finding is a homogeneous soft-tissue mass in the lower hemithorax. However, these lesions can also occur in the mediastinum, within the diaphragm, and, rarely, below the diaphragm. Radiologic diagnosis rests on identification of the systemic vascular supply. Although angiography has been routinely used in the past in evaluating these lesions, other modalities including ultrasound, computed tomography, and magnetic resonance imaging may demonstrate the anomalous feeding and draining vessels. Treatment of extralobar sequestration consists of surgical excision of the mass. Prognosis is usually favorable in the absence of associated congenital anomalies.