label: Progressive massive fibrosis
label_lc: progressive massive fibrosis
description: "This condition is caused by slow-growing conglomeration of dust particles and collagen deposition in individuals (mostly coal workers) heavily exposed to inorganic dust. Progressive massive fibrosis manifests as masslike lesions, usually bilateral and in the upper lobes. Background nodular opacities reflect accompanying pneumoconiosis, with or without emphysematous destruction adjacent to the massive fibrosis. Lesions similar to progressive massive fibrosis sometimes occur in other conditions, such as sarcoidosis and talcosis."