Usual interstitial pneumonia

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Usual interstitial pneumonia, abbreviated UIP, is common diffuse lung disease. Overall, it is uncommon.

General

  • It is sometimes used incorrectly as a synonym for idiopathic pulmonary fibrosis. It is a histomorphologic pattern and has a DDx (see below).
  • UIP cannot be diagnosed via bronchoscopic or transbronchial biopsy,[1] as it is peripheral.

Epidemiology

  • Disease of the old - rare in under 50 years old.[2]
  • Dismal prognosis - mean survival after diagnosis ~ 2.8 years.[3]

Radiology

  • Honeycombing - multiple defects that obliterate the normal lung architecture - multiple spherical voids in the lung parenchyma; radiologically these are seen as lucencies.[4]
    • Usually subplural, i.e. peripheral lung.
    • Classically lower lobe predominant.
  • Traction bronchiectasis.

Note:

  • Cysts - have thin walls (think of emphysema, lymphangioleiomyomatosis et cetera).
    • Cysts may be isolated/not close to a neighbour.
    • Medcyclopaedia defines it as: thin-walled, well-demarcated and >1 cm.[5]

Microscopic

Features:[6]

  • Fibroblast foci:
    • "Crescent-shaped bulge" of fibroblasts -- a rounded projection of spindle cells into the airspace.
    • Location: in the areas of transisition between active inflammation and old inflammation.[7]
    • Note: Technically, fibroblast foci are composed of myofibroblasts.[8]
  • Interstitial inflammation.
  • Microscopic honeycombing.
    • Typically peripheral - cysts lined by ciliated epithelium.
  • Spatial heterogeneity - patchy lesional distribution (areas of abnormal and normal lung may appear beside one another).
  • Temporal heterogeneity - lesions of differing age side-by-side.[9]

Notes:

  • Disease worse distant from large airways: lower lung field predominance, typically worse at periphery of lobule and lung.[10]
  • Heterogeneity of inflammation: airspace macrophages & inflammation minimal in honeycombed foci.

DDx of UIP:[11]

  • Idiopathic pulmonary fibrosis (UIP not otherwise specified).
  • Asbestosis = UIP pattern + ferruginous bodies with asbestos fibers.
  • Chronic hypersensitivity pneumonitis (AKA extrinsic allergic alveolitis) - classically centrilobular predominant +/- granulomas.
  • Collagen vascular disease - includes systemic lupus erythematosus, rheumatoid arthritis, scleroderma.[12]
  • Chronic drug toxicity.[13]

Images

  • UIP - fibrosis - low mag. (WC)

  • UIP - honeycomb change in UIP - low mag. (WC)

  • UIP - fibroblast focus - high mag. (WC)

See also

References

  1. ↑ Leslie, Kevin O.; Wick, Mark R. (2004). Practical Pulmonary Pathology: A Diagnostic Approach (1st ed.). Churchill Livingstone. pp. 186. ISBN 978-0443066313.
  2. ↑ AC UBC S.102.
  3. ↑ Bjoraker, JA.; Ryu, JH.; Edwin, MK.; Myers, JL.; Tazelaar, HD.; Schroeder, DR.; Offord, KP. (Jan 1998). "Prognostic significance of histopathologic subsets in idiopathic pulmonary fibrosis.". Am J Respir Crit Care Med 157 (1): 199-203. PMID 9445300.
  4. ↑ http://www.medcyclopaedia.com/library/topics/volume_v_1/h/honeycombing.aspx
  5. ↑ http://www.medcyclopaedia.com/library/topics/volume_v_1/l/lung_cyst.aspx
  6. ↑ Leslie, Kevin O.; Wick, Mark R. (2004). Practical Pulmonary Pathology: A Diagnostic Approach (1st ed.). Churchill Livingstone. pp. 186-9. ISBN 978-0443066313.
  7. ↑ http://www.epler.com/IPFWhat%27sIPFDiseaseInformation2.htm
  8. ↑ Leslie, Kevin O.; Wick, Mark R. (2004). Practical Pulmonary Pathology: A Diagnostic Approach (1st ed.). Churchill Livingstone. pp. 189. ISBN 978-0443066313.
  9. ↑ Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 92. ISBN 978-0781765275.
  10. ↑ A. Churg. UBC S.103.
  11. ↑ Wick, Mark R.; Leslie, Kevin (2005). Practical pulmonary pathology: a diagnostic approach. Edinburgh: Churchill Livingstone. ISBN 0-443-06631-0. OCLC 156861539.
  12. ↑ 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. 374. ISBN 978-1416054542.
  13. ↑ Rossi SE, Erasmus JJ, McAdams HP, Sporn TA, Goodman PC (2000). "Pulmonary drug toxicity: radiologic and pathologic manifestations". Radiographics : a review publication of the Radiological Society of North America, Inc 20 (5): 1245-59. PMID 10992015.
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