Congenital malformations
_Cystic adenomatoid malformations
�Maturation arrest in lung segments
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_Azyous lobe
�Superior apical bronchus grows medially instead of laterally; vein is at bottom of superior lobe fissure
_Sequestration –
�Accessory piece of lung that becomes disconnected from tracheobronchial tree and parasitizes systemic circulation from diaphragm.