title: Pathology of small airways disease.
abstract: BACKGROUND
  The term small airways disease encompasses a generally poorly understood group of lung diseases that may arise primarily within the small airways or secondarily from diseases primarily affecting the bronchi or lung parenchyma. Their histology may be confusing; however, because treatments and prognoses vary, correct pathologic diagnosis is important.
  
  
  OBJECTIVE
  To present a nonexhaustive review of the pathology of primary and secondary small airways diseases, including small airways disease related to tobacco; to various other exposures, including mineral dusts; to diseases involving other areas of the lung with secondary bronchiolar involvement; and to recently described bronchiolitic disorders.
  
  
  METHODS
  Current literature is reviewed.
  
  
  CONCLUSIONS
  Small airways diseases include a wide variety of diseases of which the pathologist must consider. Uncommon conditions such as diffuse idiopathic neuroendocrine cell hyperplasia and diffuse panbronchiolitis may show relatively specific diagnostic features histologically; however, most small airways diseases exhibit nonspecific histologic features. Conditions not considered primary pulmonary diseases, such as collagen vascular diseases, bone marrow transplantation, and inflammatory bowel disease, must also be considered in patients with small airways changes histologically. Clinical and radiologic correlation is important for obtaining the best possible diagnosis.
authors.affiliation: Department of Pathology, The University of Texas Health Science Center at Tyler, Tyler, TX 75708-3154, USA. timothy.allen@uthct.edu
authors.forename: Timothy Craig
authors.initials: TC
authors.lastname: Allen
mesh_terms: D001988:Bronchiolitis / Q000473:pathology*; D003937:Diagnosis, Differential; D006801:Humans; D008168:Lung / Q000473:pathology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000473:pathology*