Histopathology of Explanted Lungs From Patients With a Diagnosis of Pulmonary Sarcoidosis

Abstract

Background Pathologic features of end-stage pulmonary sarcoidosis (ESPS) are not well defined; anecdotal reports have suggested that ESPS may mimic usual interstitial pneumonia (UIP). We hypothesized that ESPS has distinct histologic features. Methods Twelve patients who received a diagnosis of pulmonary sarcoidosis and underwent lung transplantation were included. Control subjects were 10 age- and sex-matched lung transplant patients with UIP. Hematoxylin and eosin-stained tissue sections were examined for the following features: extent/pattern of fibrosis; presence and quantity (per 10 high-power fields) of fibroblast foci and granulomas; distribution and morphology of granulomas; and presence and extent of honeycomb change. Extent of fibrosis and honeycomb change in lung parenchyma was scored as follows: 1 = 1% to 25%; 2 = 26% to 50%; 3 = 51% to 75%; 4 = 76% to 100% of lung parenchyma. Results Eight of 12 cases demonstrated histologic findings typical of ESPS. All showed well-formed granulomas with associated fibrosis distributed in a distinct lymphangitic fashion. Granulomas were present in hilar or mediastinal lymph nodes from six of six patients with ESPS and none of eight control subjects. The extent of fibrosis, honeycomb change, and fibroblast foci was significantly lower in ESPS cases compared with control cases. Two patients with remote histories of sarcoidosis showed histologic features of diseases other than ESPS (UIP and emphysema) without granulomas. Two patients with atypical clinical findings demonstrated nonnecrotizing granulomas combined with either severe chronic venous hypertension or UIP. Conclusions ESPS and UIP have distinct histopathologic features in the lungs. Patients with a pretransplant diagnosis of sarcoidosis may develop other lung diseases that account for their end-stage fibrosis.