Interstitial Pneumonias

Usual interstitial pneumonia (UIP)

UIP is characterized by patchy architectural distortion (honeycombing at lower left). This view also shows fibrosis radiating from bronchovascular bundles (B), interlobular septa (S), and the pleura (left).

Must have Honeycombing, Old fibrosis, Recent granulation tissue, and Normal lung (HORN).

Usual interstitial pneumonia

Black arrow--Normal lung

Green arrow--Alveolitis: alveolar wall thickening, interstitial inflammation, type II cell hyperplasia

Brown arrow--Confluent alveolitis

Blue arrow--Fibrosis

The cellular, bluish, granulaton tissue here contrasts with the dense, pink fibrous tissue at the lower left. Together they indicate temporal heterogeneity.

Emphysema versus honeycombing

Left: Emphysematous spaces with thin walls

Right: Honeycombed spaces with thick walls adjacent to normal lung (arrow)

See also Case 27