End-stage sarcoid lung disease is distinct from usual interstitial pneumonia

Sarcoid lung disease may result in progressive lung failure, necessitating transplant. There is a debate on whether the scarring is similar to or distinct from that seen in other fibrotic lung disease such as usual interstitial pneumonia (UIP). We prospectively evaluated histologic sections from 9 lung explants with end-stage sarcoid lung disease diagnosed clinically and by chest computed tomographic scans. The study included 7 women and 2 men. Four lungs showed active granulomatous disease, with nonfibrotic nodular granulomas in the interstitium; the other 5 were predominantly fibrotic, of which 3 had areas of honeycombing (cysts lined by respiratory epithelium with surrounding scar). Chest computed tomographs of 8 cases were all read as either probable or definite sarcoid. Patients in the fibrotic phase were significantly older (P=0.016). All cases showed dense acellular collagen, which was more extensive in the fibrotic phase. Granulomas were present in a lymphatic distribution (along bronchi, the lobular septa, and the pleura) and were predominantly small clusters of macrophages or giant cells embedded in scar in the fibrotic phase. Granulomas were not identified in 2 lungs in the fibrotic phase. In contrast to the honeycombing of UIP, the honeycombing was predominantly central, with prominent bronchiectasis. These end-stage sarcoid lungs were characterized by a fibrotic and active granulomatous pattern, both of which are very distinct from that seen in UIP.