Sarcoidosis is a granulomatous disorder of unknown cause. Non-caseating granulomas may form in any body tissue and the lungs are frequently affected. Granulomas form along the pulmonary lymphatics, so the distribution of nodularity is often centrilobular and subpleural.  Granulomas can coalesce to form fibrous masses and regions of dense consolidation in the lungs which are centered around the perihilar bronchi and vessels, usually in the upper lobes.  Pulmonary sarcoidosis progresses to fibrosis in 20-25% of patients and the fibrosis will remain once the disease is no longer active.  

Airway occlusion and stenosis occur either due to compression by adjacent lymph nodes or distortion due to fibrosis, as in this case, or granulomas within the airways that become fibrotic over time.

When granulomas within lymph nodes start to calcify, the calcification is very fine and powdery – described as ‘icing sugar’.  The calcification gradually becomes more coarse and increases in density over time.