Secondary Bronchomalacia may occur by extrinsic compression from an enlarged vessel, a vascular ring or a bronchogenic cyst.

Bronchogenic cysts are small, solitary cysts or sinuses, most typically located in the region of the suprasternal notch or over the manubrium.

Less common causes of a solitary pulmonary nodule include hamartomas, bronchogenic cysts, adenomas, arteriovenous malformation, pulmonary sequestration, rheumatoid nodules, Wegener's granulomatosis, or lymphoma.