Congenital respiratory cyst. RPC from the AFIP.

The radiologic finding of a thin-walled cystic structure in the lung should raise the question of a possible congenital respiratory cyst. This is often a difficult diagnosis to confirm, and the presence of radiologic findings such as loculation of the cyst, ill-defined or shaggy borders, interstitial reticulations, or pleural thickening should all be considered suggestive of postinflammatory processes such as abscess, cystic bronchiectasis, or even tuberculosis. A history of previous pneumonia should also be considered evidence to question the diagnosis of congenital respiratory cyst and suggest the possibility of a pneumatocele.