Pulmonary pathology

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The lung is a forgotten organ in pathology, 'cause radiologists can diagnose much with high resolution CT (HRCT) and a bit of history. This article introduces the lung and discusses an approach to the lung.

Medical lung disease is dealt with in the medical lung disease article. Tumours of the lung are dealt with in lung tumours article. Lung cytopathology is dealt with in the pulmonary cytopathology article.

Basic approach

All lung pathology can be grouped into one of six categories (as per Leslie). The radiology directly correlates to the pathologic grouping, except that air space disease encompasses three pathologic categories (ALI, CCI, AFD).

Pathologic groups:

 
 
 
 
 
 
 
 
 
 
Lung pathology
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Acute lung
injury
 
Fibrosis
 
Chronic cellular
infiltrates (ALI)
 
Alveolar filling
defect (AFD)
 
Nodules
 
Near normal
histology


Identification of the groups:

  • Acute lung injury: hyaline membranes (very pink on H&E).
  • Fibrosis = thick walls - pink on H&E.
  • Chronic cellular infiltrates = inflammation (blue on H&E).
  • Nodules = look at the history/radiology - should say mass or nodule.
  • Alveolar filling defect = crap in the alveoli.
  • Near normal = looks almost normal.


Radiologic groups:

 
 
 
 
 
 
Lung radiology
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Air space
disease
 
Interstitial
disease
 
Mass/nodules
 
Near normal


Radiologic-pathologic correlation:

  • Air space disease (radiologic).
    • Acute lung injury.
    • Chronic cellular infiltrates.
    • Alveolar filling defects.
  • Interstitial disease (radiologic).
    • Fibrosis.
  • Mass/nodules (radiologic).
    • Nodules.
  • Near normal (radiologic).
    • Near normal histology.

Most of the things that come to pathology are in the mass/nodules category and lung tumours (discussed below). The other categories are dealt with in the medical lung disease article.

Anatomical approach:

  • Pleura - thickening?
  • Airspace - filling?
  • Alveolar walls - thickening?
  • Airways - inflammation?
  • Vessels - thickening?

Normal histology

Cells

Common:

  • Type I pneumocyte - cover most of the alveolar surface.
  • Type II pneumocyte - stem cell, produce surfactant.
    • Typical location: "angle of alveolus".
  • Macrophages.

Rare:

  • Pulmonary neuroendocrine cells:[1]
    • Histomorphology:
      • Single cells.
      • Small clusters ~ 6 cells ("neuroepithelial bodies").
    • Identified with immunostains:
      • Serotonin.
      • Bombesin.
      • Chromogranin A.
      • Synaptic vesicle 2.

Lung lobule

Lung lobule:[2]

  • Arterial vessels travels with the bronchus.
  • Venules travel in the septae.
  • Arterial vessels in the lung should be approximately the same size as its accompanying airway.[3]

Memory device: arteries (which were once thought to contain air) are with the airway.

Small airways

The trip to the alveolus:[4]

  1. Membranous bronchiole.
  2. Terminal bronchiole - dilation distal to this = emphysema.
  3. Respiratory bronchiole.
  4. Alveolar duct - dilated in ARDS.
  5. Alveolus.

Anatomy - terms

  • Bronchus = has cartilage.
  • Bronchiole = non-cartilaginous airway.

Pathology terminology

  • Siderophages = mononuclear phagocyte with hemosiderin.[5]
  • Hyaline membrane = glassy layering of an alveolus/small airways with material that is eosinophilic on H&E.[6]
  • Smoker's macrophages = brown-pigmented macrophages - assoc. with smoking.[8]

Malignancy - lung cancer

Main article: Lung cancer

This often comes to the pathologist.

Medical lung disease

Main article: Medical lung disease

Includes discussion of things like acute infectious pneumonia and idiopathic pulmonary fibrosis.

Pulmonary hypertension is dealt with in its own article pulmonary hypertension.

Lung transplant pathology

Main article: Lung transplant pathology

Bronchogenic cyst

General

  • Benign.
  • Usually in mediastinum or hilum.[9]
  • Fit into the bigger category of foregut cyst.

Microscopic

Features:[10]

  • Cyst lined by respiratory epithelium.

Images:

Pulmonary hamartoma

General

  • Benign.

See also: Hamartoma.

Gross

  • Well circumscribed lesion.

Microscopic

Features:

  • Cartilage - key feature.
    • Single cells in lacunae surrounded by abundant matrix.
      • Paucicellular vis-a-vis malignant lesions.
  • Fat (adipocytes) - key feature.
  • Respiratory epithelium (columnar epithelium with cilia).

Notes:

  • No nuclear atypia.

Images:

Malformations

Come in three flavours:

  1. Congenital pulmonary airway malformation (CPAM).
  2. Extralobar sequestration (ELS).
  3. Intralobar sequestrations (ILS).

Congenital pulmonary airway malformation

  • Previously known as congenital cystic adenomatoid malformation (CCAM).[12]

General:

  • Classified according to density:[13]
    • Type I = mostly large cysts.
    • Type II = mostly small cysts.
    • Type III = solid mass.

Microscopic

Features:[13]

  • Irregular cystic spaces with bronchial epithelium.
    • Bronchial epithelium = cilia, pseudostratified.

Extralobar sequestration

General:

  • Typically not connected to airway tree/trachea.
  • Blood supply arises from aorta, not the pulmonary artery.
  • Mass lesion.
  • Associated with other congenital anomalies.[9] The most common are diaphragmatic abnormalities - including congenital diaphragmatic hernia.[14]

Microscopic

Features:[13]

  • Abnormal airways:
    • Dilated irregularly shaped bronchi.
      • Wavy luminal contour/undulating contour (normal ~ round/ovoid).
    • Distal airways with ciliated epithelium.
  • +/-Infection.
    • +/-Interstitial fibrosis due to inflammation.

Image:

Intralobar sequestration

General:

  • Classically identified due to recurrent infections or bronchiectasis.[9]
  • Intralobular sequestration can be considered a variant of ELS; it is like an ELS but surrounded by normal lung.

Bronchopulmonary dysplasia

  • Abbreviated BPD.

General

  • Developmental.
  • Assoc. with prematurity.[15]

Microscopic

Features:

  • Large alveoli.
  • Bronchiolar fibrosis.
  • Interstitial fibrosis.

Images:

See also

References

  1. ↑ Cutz E, Yeger H, Pan J (2007). "Pulmonary neuroendocrine cell system in pediatric lung disease-recent advances". Pediatr. Dev. Pathol. 10 (6): 419–35. doi:10.2350/07-04-0267.1. PMID 18001162.
  2. ↑ http://lib.hku.hk/denlib/exhibition/rarebook/mouth_hygiene_plate.jpg
  3. ↑ Leslie, Kevin O.; Wick, Mark R. (2004). Practical Pulmonary Pathology: A Diagnostic Approach (1st ed.). Churchill Livingstone. pp. 266. ISBN 978-0443066313.
  4. ↑ Hegele. 27 October 2009.
  5. ↑ http://medical-dictionary.thefreedictionary.com/siderophore
  6. ↑ http://medical-dictionary.thefreedictionary.com/hyaline+membrane
  7. ↑ http://pathhsw5m54.ucsf.edu/case27/image277.html
  8. ↑ Leslie, Kevin O.; Wick, Mark R. (2004). Practical Pulmonary Pathology: A Diagnostic Approach (1st ed.). Churchill Livingstone. pp. 236. ISBN 978-0443066313.
  9. ↑ 9.0 9.1 9.2 Mitchell, Richard; Kumar, Vinay; Fausto, Nelson; Abbas, Abul K.; Aster, Jon (2011). Pocket Companion to Robbins & Cotran Pathologic Basis of Disease (8th ed.). Elsevier Saunders. pp. 363. ISBN 978-1416054542.
  10. ↑ Chen, C.; Zheng, H. (Jun 2008). "Extralobar pulmonary sequestration in the hilum.". Asian Cardiovasc Thorac Ann 16 (3): 246-8. PMID 18515678. http://asianannals.ctsnetjournals.org/cgi/content/full/16/3/246.
  11. ↑ URL: http://www.path.utah.edu/casepath/pm%20cases/pmcase8/pmcase8part4.htm. Accessed on: 9 June 2011.
  12. ↑ URL: http://radiopaedia.org/articles/congenital-pulmonary-airway-malformation. Accessed on: 10 February 2012.
  13. ↑ 13.0 13.1 13.2 Klatt, Edward C. (2006). Robbins and Cotran Atlas of Pathology (1st ed.). Saunders. pp. 100. ISBN 978-1416002741.
  14. ↑ Rosado-de-Christenson, ML.; Frazier, AA.; Stocker, JT.; Templeton, PA. (Mar 1993). "From the archives of the AFIP. Extralobar sequestration: radiologic-pathologic correlation.". Radiographics 13 (2): 425-41. PMID 8460228. http://radiographics.rsnajnls.org/cgi/pmidlookup?view=long&pmid=8460228.
  15. ↑ Chang, LW. (Sep 2011). "[Incidence and risk factors of bronchopulmonary dysplasia in premature infants in 10 hospitals in China].". Zhonghua Er Ke Za Zhi 49 (9): 655-62. PMID 22176899.

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