Areas of lung overexpansion alternate with fibrosed, restricted lung. This results in a typical cobblestone appearance. This entity, which follows hyaline membrane disease, is seen much less frequently with the use of surfactant in the care of premature infants.
Microscopically, BPD shows fibrosis in interstitium of septal walls and elsewhere as seen on the left with a trichrome stain. On the right, one sees hyperplasia of cuboidal epithelium lining the airspaces.