A number of lung diseases, both focal and diffuse, result in pulmonary fibrosis. Fibrosis can represent cellular fibrous tissue characterized by fibroblast proliferation or dense acellular collagenous tissue. Fibrosis can result in reticular, nodular or stellate opacities on radiographs or CT, associated with volume loss in affected lung and architectural distorsion. It may remain stable over months or years or show progression.Focal fibrosis is often referred to as scarring. Fibrosis adjacent to tumours or inflammatory lesions may give them a stellate or irregular appearance termed a corona radiata. A number of diffuse lung diseases result in diffuse fibrosis. Honeycombing is one such pattern of diffuse fibrosis. Other patterns of fibrosis include conglomerate masses in silicosis or sarcoidosis, and traction bronchiectasis.
