Progressive massive fibrosis (PMF) refers to the formation of large mass-like conglomerates, predominantly in the upper pulmonary lobes, associated with radiating strands. These classically develop in the context of certain pneumoconioses (especially Coal worker's pneumoconiosis and silicosis) although similar mass-like densities have occasionally been described with talcosis.
Mass-like areas of lung opacification associated with radiating strands are seen; the "sausage-shaped" mass is characteristic. These regions commonly contain air bronchograms and calcifications 4. These areas can shrink over time and migrate towards the hilar regions 5.
Magnetic resonance imaging can be helpful for distinguishing between progressive massive fibrosis and lung cancer 3. The latter typically appears as T2-bright, whereas progressive massive fibrosis appears as T2-dark (compared to skeletal muscle)3.
The most frequent MRI appearance are regions which have following signal characteristics 1-2:
- T1: iso- to hyperintense
- hypointense (compared with skeletal muscle)
- areas of internal high T2 signal
- there may be rim enhancement
On PET-CT, progressive massive fibrosis can be FDG-avid 3.
Possible differential considerations include:
- 1. Matsumoto S, Mori H, Miyake H et-al. MRI signal characteristics of progressive massive fibrosis in silicosis. Clin Radiol. 1998;53 (7): 510-4. Pubmed citation
- 2. Jung JI, Park SH, Lee JM et-al. MR characteristics of progressive massive fibrosis. J Thorac Imaging. 2000;15 (2): 144-50. Pubmed citation
- 3. Chong S, Lee KS, Chung MJ et-al. Pneumoconiosis: comparison of imaging and pathologic findings. Radiographics. 2006;26 (1): 59-77. Radiographics (full text) - doi:10.1148/rg.261055070 - Pubmed citation
- 4. Ferreira AS, Moreira VB, Ricardo HM et-al. Progressive massive fibrosis in silica-exposed workers. High-resolution computed tomography findings. J Bras Pneumol. 2007;32 (6): 523-8. Pubmed citation
- 5. Lange S. Radiology of Chest Diseases. Thieme Medical Publishers. (1998) ISBN:1588904474. Read it at Google Books - Find it at Amazon
- 6. Mueller-Mang C, Grosse C, Schmid K et-al. What every radiologist should know about idiopathic interstitial pneumonias. Radiographics. 2007;27 (3): 595-615. Radiographics (full text) - doi:10.1148/rg.273065130 - Pubmed citation
- 7. Wang Y, Zhang H, Cui X et-al. Clinical value of (18)F-FDGPET/CT in differentiation between benign lesions and lung cancer for large shadows in patients with pneumoconiosis. Zhonghua Lao Dong Wei Sheng Zhi Ye Bing Za Zhi. 2015;32 (3): 186-9. Pubmed citation