The crossover lung segment: congenital malformation associated with a variant of scimitar syndrome.

Three cases of a congenitally misplaced segment of lung are described. In one case the abnormal segment was identified at thoracotomy; it extended from an origin in the right upper lobe across the midline into the left hemithorax. The remaining two patients, with identical radiographic features, were identified in a review of 24 cases of bronchovascular malformation. In all three patients the crossover segment was associated with a variant of the scimitar syndrome: right lung hypoplasia with dextrocardia, aberrant systemic arterial supply to the right lower lobe, and anomalous venous drainage of the whole of the right lung, and in two patients with eventration of the right diaphragm.