Usual interstitial pneumonia

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Usual interstitial pneumonia, abbreviated UIP, is a relatively common pattern in diffuse lung diseases. Overall, it is an uncommon pathology.

Usual interstitial pneumonia
Diagnosis in short

Fibroblast focus in usual interstitial pneumonia. H&E stain.
LM fibroblast foci, interstitial inflammation, microscopic honeycombing (typically peripheral & 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
LM DDx asbestosis, chronic hypersensitivity pneumonitis, collagen vascular disease (e.g. systemic lupus erythematosus, rheumatoid arthritis, scleroderma), chronic drug toxicity
Stains iron stain -ve
Gross lower lobe & periperal predominant: fibrosis, peripheral cysts
Site lung - see diffuse lung diseases
Signs signs of right heart failure
Symptoms shortness of breath
Prevalence uncommon
Radiology interstitial pattern, lower lobe predominant, peripheral cysts
Prognosis usually poor, dependent on amount of fibrosis
Other histologic correlate of idiopathic pulmonary fibrosis
Clin. DDx asbestosis, chronic hypersensitivity pneumonitis, collagen vascular disease (history missing), chronic drug toxicity (history missing), idiopathic pulmonary fibrosis
Treatment lung transplantation

Idiopathic pulmonary fibrosis (abbreviated IPF) redirects here.

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]

Images

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

  • UIP - fibrosis - low mag. (WC)

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

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A. Lung, Right Lower Lobe, Wedge Biopsy:
	- Usual interstitial pneumonia, see comment and microscopic.

B. Lung, Right Middle Lobe, Wedge Biopsy:
	- Usual interstitial pneumonia, see comment and microscopic.

C. Lung, Right Upper Lobe, Wedge Biopsy:
	- Usual interstitial pneumonia, see comment and microscopic.

Comment:
There are no findings to specifically suggest hypersensitivity. Clinical and radiologic 
correlation is suggested.

Alternate

Right Lower Lobe of Lung, Wedge Resection:
     - Usual interstitial pneumonia (UIP) pattern (fibroblast foci, bronchiolization, 
       extensive fibroelastotic scarring and focal calcification/bone formation), see comment.

Comment:
UIP pattern may be idiopathic. It is also be seen in the context of collagen vascular diseases, hypersensitivity reactions, and drugs; these need to be considered in clinical context along with the imaging findings.

Micro

Sections show lung parenchyma with:
Fibrosis (severity; lobar location): present (moderate-to-severe; peripheral predominant).
Fibrosis - lung field predominance: lower lobe > middle lobe > upper lobe. 
Fibroblast foci: present.
Temporal heterogeneity: present.
Spatial heterogeneity: present.
Peripheral cyst formation: present.
Inflammation: present - patchy, lymphocyte predominant.
Granulomatous inflammation: absent.
Blood vessel changes: present, moderate-to-severe.
Airspace changes: mucous plugs.

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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