The differential for tracheal mural thickening includes:

• circumferential thickening
  • infectious - TB / Aspergillus
  • granulomatosis with polyangiitis 
  • amyloidosis
  • sarcoidosis
• eccentric thickening / mass-like
  • primary malignancy, e.g. squamous cell carcinoma (SCC), adenoid cystic carcinoma
  • metastases
  • carcinoid
• spares the posterior tracheal muscle
  • tracheobronchopathia osteochondroplasia
  • relapsing polychondritis