Progressive massive fibrosis
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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.
May be seen as large symmetric bilateral opacities with irregular margins in the upper lobes 3.
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 T2 hyperintense, whereas progressive massive fibrosis appears T2 hypointense (compared to skeletal muscle) 3.
Lesions most frequently have the following signal characteristics 1,2:
T1: iso- to hyperintense
hypointense (compared with skeletal muscle)
areas of internal high T2 signal
T1 C+ (Gd): may show rim enhancement 8
On PET-CT, progressive massive fibrosis can be FDG-avid 3.
Possible differential considerations include:
In some situations consider pulmonary manifestations of sarcoidosis.
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