Pulmonary sequestration-like anomaly presenting as a spontaneously resolving mass

A premature baby boy presented at birth with respiratory distress. A right lower lobe opacity was found on chest X-ray. Pulmonary sequestration was the diagnosis suggested by ultrasound. The size of the mass decreased on subsequent examinations. 4 months later X-rays and sonography failed to demonstrate any remaining mass. This case illustrates another example of involutive pathology and suggests that not all pulmonary sequestration-like anomalies should be operated on.