Difference between revisions of "Diffuse lung diseases"

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An introduction to pulmonary pathology is found in the ''[[pulmonary pathology]]'' article.
An introduction to pulmonary pathology is found in the ''[[pulmonary pathology]]'' article.


=Overview - histologic classification=
=Overview=
==Specimens==
*Diffuse lung disease is best assessed on an open biopsy.
**These procedure are quite invasive; thus, not infrequently clinicians will try a transbrochial biopsy that ends-up providing in useful information.
 
===Sign out===
<pre>
LUNG, LEFT, TRANSBRONCHIAL BIOPSY:
- SMALL FRAGMENTS OF LUNG PARENCHYMA WITHOUT SIGNIFICANT CHANGES, SEE MICROSCOPIC
  DESCRIPTION AND COMMENT.
 
COMMENT:
The clinical findings are noted. The size and type of biopsy significantly limit the
interpretation.  Suspected diffuse lung disease (interstitial lung disease)
is best assessed on an open lung biopsy.
</pre>
====Micro====
The sections show small fragments of lung parenchyma. A very small amount of anthracotic
pigment is present. Interstitial fibrosis is not apparent. No granulomata are identified.
No nuclear atypia is identified. Air-space macrophages show minimal pigmentation and are
not present in large numbers. No significant airspace or interstitial inflammation is
identified.
 
==Histologic classification==
*Can be complex,<ref name="pmid12405906">{{cite journal |author=Nicholson AG |title=Classification of idiopathic interstitial pneumonias: making sense of the alphabet soup |journal=Histopathology |volume=41 |issue=5 |pages=381-91 |year=2002 |month=November |pmid=12405906 |doi= |url=http://www3.interscience.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=0309-0167&date=2002&volume=41&issue=5&spage=381}}</ref> and the combined efforts of [[clinician]]s, [[radiologist]]s, and [[pathologist]]s can help in the generation of a more specific diagnosis.<ref name="pmid15256390">{{cite journal |author=Flaherty KR, King TE, Raghu G, ''et al'' |title=Idiopathic interstitial pneumonia: what is the effect of a multidisciplinary approach to diagnosis? |journal=Am. J. Respir. Crit. Care Med. |volume=170 |issue=8 |pages=904-10 |year=2004 |month=October |pmid=15256390 |doi=10.1164/rccm.200402-147OC |url=http://ajrccm.atsjournals.org/cgi/pmidlookup?view=long&pmid=15256390}}</ref><ref name="pmid16738191">{{cite journal |author=Kim DS, Collard HR, King TE |title=Classification and natural history of the idiopathic interstitial pneumonias |journal=Proc Am Thorac Soc |volume=3 |issue=4 |pages=285-92 |year=2006 |month=June |pmid=16738191 |doi=10.1513/pats.200601-005TK |url=http://pats.atsjournals.org/cgi/pmidlookup?view=long&pmid=16738191}}</ref>
*Can be complex,<ref name="pmid12405906">{{cite journal |author=Nicholson AG |title=Classification of idiopathic interstitial pneumonias: making sense of the alphabet soup |journal=Histopathology |volume=41 |issue=5 |pages=381-91 |year=2002 |month=November |pmid=12405906 |doi= |url=http://www3.interscience.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=0309-0167&date=2002&volume=41&issue=5&spage=381}}</ref> and the combined efforts of [[clinician]]s, [[radiologist]]s, and [[pathologist]]s can help in the generation of a more specific diagnosis.<ref name="pmid15256390">{{cite journal |author=Flaherty KR, King TE, Raghu G, ''et al'' |title=Idiopathic interstitial pneumonia: what is the effect of a multidisciplinary approach to diagnosis? |journal=Am. J. Respir. Crit. Care Med. |volume=170 |issue=8 |pages=904-10 |year=2004 |month=October |pmid=15256390 |doi=10.1164/rccm.200402-147OC |url=http://ajrccm.atsjournals.org/cgi/pmidlookup?view=long&pmid=15256390}}</ref><ref name="pmid16738191">{{cite journal |author=Kim DS, Collard HR, King TE |title=Classification and natural history of the idiopathic interstitial pneumonias |journal=Proc Am Thorac Soc |volume=3 |issue=4 |pages=285-92 |year=2006 |month=June |pmid=16738191 |doi=10.1513/pats.200601-005TK |url=http://pats.atsjournals.org/cgi/pmidlookup?view=long&pmid=16738191}}</ref>


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| [[Desquamative interstitial pneumonia]] (DIP)
| [[Desquamative interstitial pneumonia]] (DIP)
| DIP
| DIP
| Smoking
| [[smoking]]
|-
|-
| [[Diffuse alveolar damage]] (DAD)
| [[Diffuse alveolar damage]] (DAD)
Line 32: Line 56:
| [[Respiratory bronchiolitis]]  
| [[Respiratory bronchiolitis]]  
| [[Respiratory bronchiolitis-associated interstitial lung disease|RB-ILD]]
| [[Respiratory bronchiolitis-associated interstitial lung disease|RB-ILD]]
| Smoking
| smoking
|-
|-
| [[Usual interstitial pneumonia]] (UIP)
| [[Usual interstitial pneumonia]] (UIP)
| [[collagen vascular disease|CVD]], [[idiopathic pulmonary fibrosis|IPF]], [[drug toxicity]], [[pneumoconiosis]]
| [[collagen vascular disease|CVD]], [[idiopathic pulmonary fibrosis|IPF]], [[drug toxicity]], [[pneumoconiosis]]
| Allergen (hypersensitivity pneumonitis), idiopathic, autoimmune
| allergen (hypersensitivity pneumonitis), idiopathic, autoimmune
|-
|-
| [[Organizing pneumonia]]
| [[Organizing pneumonia]]
Line 44: Line 68:
| [[Lymphocytic interstitial pneumonia]] (LIP)
| [[Lymphocytic interstitial pneumonia]] (LIP)
| LIP
| LIP
| Viral/autoimmune
| viral/autoimmune
|}
|}
ARDS = adult respiratory distress syndrome, AIP = acute interstitial pneumonia, TRALI = transfusion related acute lung injury, CVD = [[collagen vascular disease]], IPF = idiopathic pulmonary fibrosis.
ARDS = adult respiratory distress syndrome, AIP = acute interstitial pneumonia, TRALI = transfusion related acute lung injury, CVD = [[collagen vascular disease]], IPF = idiopathic pulmonary fibrosis.


Notes:
Notes:
*''Usual interstitial pneumonia'' is the most common type of ILD.<ref name="pmid16738196">{{cite journal |author=Visscher DW, Myers JL |title=Histologic spectrum of idiopathic interstitial pneumonias |journal=Proc Am Thorac Soc |volume=3 |issue=4 |pages=322-9 |year=2006 |month=June |pmid=16738196 |doi=10.1513/pats.200602-019TK |url=http://pats.atsjournals.org/cgi/pmidlookup?view=long&pmid=16738196}}</ref>
*''Usual interstitial pneumonia'' is the most common type of ILD.<ref name="pmid16738196">{{cite journal |author=Visscher DW, Myers JL |title=Histologic spectrum of idiopathic interstitial pneumonias |journal=Proc Am Thorac Soc |volume=3 |issue=4 |pages=322-9 |year=2006 |month=June |pmid=16738196 |doi=10.1513/pats.200602-019TK |url=http://pats.atsjournals.org/cgi/pmidlookup?view=long&pmid=16738196}}</ref>
==Gross pathologic DDx by location==
Causes of upper lung fibrosis ''FASSTEN'':<ref name=Ref_TN2005_R13>{{Ref TN2005| R13}}</ref>
*[[Farmer's lung]].
*[[Ankylosing spondylitis]].
*[[Sarcoidosis]].
*[[Silicosis]].
*[[Tuberculosis]] (miliary).
*[[Eosinophilic granuloma]].
*[[Neurofibromatosis]].
Causes of lower lung fibrosis ''BAD RASH'':<ref name=Ref_TN2005_R13>{{Ref TN2005| R13}}</ref>
*[[Bronchiolitis obliterans organizing pneumonia]] (BOOP).
*[[Asbestosis]].
*Drugs (nitrofurantoin, hydralazine, isoniazid (INH), amiodarone).
*[[Rheumatologic disease]].
*[[aspiration pneumonia|Aspiration]].
*[[Scleroderma]].
*Hamman-Rich syndrome (really should be -- ''[[idiopathic pulmonary fibrosis]]'').
Note:
*''Hamman-Rich syndrome'' is another name for [[acute interstitial pneumonia]].<ref name=Ref_WMSP90>{{Ref WMSP|90}}</ref>


=Specific diseases/pattterns=
=Specific diseases/pattterns=
Line 56: Line 101:
==Diffuse alveolar damage==
==Diffuse alveolar damage==
*Abbreviated ''DAD''.
*Abbreviated ''DAD''.
===General===
{{Main|Diffuse alveolar damage}}
Etiology:
*Abrupt hypoxemia with pulmonary infiltrates leading to epithelial cell and endothelial cell death not accompanied by cardiac failure.<ref name=Ref_PCPBoD8_364>{{Ref PCPBoD8|364}}</ref>
 
DAD is the histologic correlate of:
*Acute respiratory distress syndrome (ARDS).
**[[AKA]] adult respiratory distress syndrome (ARDS) to differentiate it from ''[[respiratory distress syndrome]]'' in infants.
*Acute interstitial pneumonia (AIP).
*Transfusion related acute lung injury (TRALI).
 
The DDx is broad:<ref>{{Ref WMSP|91}}</ref>
*Infection/sepsis.
*Toxic (smoke, oxygen).
*Drug (amiodarone, chemotherapy).
*Trauma/shock.
*Inflammatory.
*Idiopathic.
 
===Microscopic===
Features:<ref name=Ref_Klatt103>{{Ref Klatt|103}}</ref><ref name=pmid16766248>{{Cite journal  | last1 = Castro | first1 = CY. | title = ARDS and diffuse alveolar damage: a pathologist's perspective. | journal = Semin Thorac Cardiovasc Surg | volume = 18 | issue = 1 | pages = 13-9 | month =  | year = 2006 | doi = 10.1053/j.semtcvs.2006.02.001 | PMID = 16766248 }}</ref>
#Exudative:
#*Hyaline membranes - '''key feature'''.
#**Debris (pink crap) lines the alveolar spaces.
#Proliferative:
#*Interstitial thickening.
#*Inflammation (lymphocytes).
#*Hobnailing of alveolar lining cells (type 2 pneumocyte hyperplasia<ref>URL: [http://d3jonline.tripod.com/20-Pulmonary_II/Pathology_of_Interstitial_Lung_Diseases.htm http://d3jonline.tripod.com/20-Pulmonary_II/Pathology_of_Interstitial_Lung_Diseases.htm]. Accessed on: 22 February 2012.</ref>).
#*Edema (link pink crap in the alveoli).
#*[[Masson bodies]] in the airway.
#*Hyaline material (usu. focal) - '''key feature'''.
#Fibrotic:
#*Interstitial inflammation.
#*Fibrosis.
 
DDx:<ref name=pmid16766248>{{Cite journal  | last1 = Castro | first1 = CY. | title = ARDS and diffuse alveolar damage: a pathologist's perspective. | journal = Semin Thorac Cardiovasc Surg | volume = 18 | issue = 1 | pages = 13-9 | month =  | year = 2006 | doi = 10.1053/j.semtcvs.2006.02.001 | PMID = 16766248 }}</ref>
*[[Cryptogenic organizing pneumonia]] - especially for ''proliferative phase DAD''.
*[[Bronchiolitis obliterans]].
 
====Images====
<gallery>
Image:Hyaline membranes - low mag.jpg | Exudative phase DAD - low mag. (WC/Nephron)
Image:Hyaline membranes - intermed mag.jpg | Exudative phase DAD - intermed. mag. (WC/Nephron)
Image:Hyaline membranes - high mag.jpg | Exudative phase DAD - high mag. (WC/Nephron)
Image:Hyaline membranes - very high mag.jpg | Exudative phase DAD - very high mag. (WC/Nephron)
Image:ARDS.jpg | Exudative DAD (WC)
</gallery>
www:
*[http://www.flickr.com/photos/pulmonary_pathology/4710141110/in/photostream/ Proliferative phase DAD - intermed. mag. (flickr.com/Yale Rosen)].
*[http://www.flickr.com/photos/pulmonary_pathology/4709499629/in/photostream/ Proliferative phase DAD - high mag. (flickr.com/Yale Rosen)].


==Usual interstitial pneumonia==
==Usual interstitial pneumonia==
*Abbreviated ''UIP''.
*Abbreviated ''UIP''.
===General===
{{Main|Usual interstitial pneumonia}}
*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,<ref name=Ref_PPP186>{{Ref PPP|186}}</ref> as it is peripheral.
 
====Epidemiology====
*Disease of the old - rare in under 50 years old.<ref>AC UBC S.102.</ref>
*Dismal prognosis - mean survival after diagnosis ~ 2.8 years.<ref name=pmid9445300>{{Cite journal  | last1 = Bjoraker | first1 = JA. | last2 = Ryu | first2 = JH. | last3 = Edwin | first3 = MK. | last4 = Myers | first4 = JL. | last5 = Tazelaar | first5 = HD. | last6 = Schroeder | first6 = DR. | last7 = Offord | first7 = KP. | title = Prognostic significance of histopathologic subsets in idiopathic pulmonary fibrosis. | journal = Am J Respir Crit Care Med | volume = 157 | issue = 1 | pages = 199-203 | month = Jan | year = 1998 | doi =  | PMID = 9445300 }}</ref>
 
===Radiology===
*Honeycombing - ''multiple'' defects that obliterate the normal lung architecture - multiple spherical voids in the lung parenchyma; radiologically these are seen as lucencies.<ref>[http://www.medcyclopaedia.com/library/topics/volume_v_1/h/honeycombing.aspx http://www.medcyclopaedia.com/library/topics/volume_v_1/h/honeycombing.aspx]</ref>
**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.<ref>[http://www.medcyclopaedia.com/library/topics/volume_v_1/l/lung_cyst.aspx http://www.medcyclopaedia.com/library/topics/volume_v_1/l/lung_cyst.aspx]</ref>
 
===Microscopic===
Features:<ref name=Ref_PPP186-9>{{Ref PPP|186-9}}</ref>
*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.<ref>[http://www.epler.com/IPFWhat%27sIPFDiseaseInformation2.htm http://www.epler.com/IPFWhat%27sIPFDiseaseInformation2.htm]</ref>
**Note: Technically, ''fibroblast foci'' are composed of myofibroblasts.<ref name=Ref_PPP189>{{Ref PPP|189}}</ref>
*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.<ref name=Ref_WMSP92>{{Ref WMSP|92}}</ref>
 
Notes:
*Disease worse distant from large airways: lower lung field predominance, typically worse at periphery of lobule and lung.<ref>A. Churg. UBC S.103.</ref>
*Heterogeneity of inflammation: airspace macrophages & inflammation minimal in honeycombed foci.
 
DDx of UIP:<ref name=leslie>{{cite book |author=Wick, Mark R.; Leslie, Kevin |title=Practical pulmonary pathology: a diagnostic approach |publisher=Churchill Livingstone |location=Edinburgh |year=2005 |pages= |isbn=0-443-06631-0 |oclc= 156861539|doi= |accessdate=}}</ref>
*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]].<ref name=Ref_PCPBoD8_374>{{Ref PCPBoD8|374}}</ref>
*Chronic drug toxicity.<ref name=pmid10992015>{{cite journal |author=Rossi SE, Erasmus JJ, McAdams HP, Sporn TA, Goodman PC |title=Pulmonary drug toxicity: radiologic and pathologic manifestations |journal=Radiographics : a review publication of the Radiological Society of North America, Inc |volume=20 |issue=5 |pages=1245-59 |year=2000 |pmid=10992015 |doi=}}</ref>


==Asbestosis==
==Asbestosis==
===General===
{{Main|Asbestosis}}
Definition:
*Interstitial lung disease due to asbestos exposure.<ref name=Ref_PCPBoD8_375>{{Ref PCPBoD8|375}}</ref>
**Important to diagnose... asbestosis = compensation.
 
Conditions associated with asbestos exposure (mnemonic ''PALM''):<ref name=Ref_PCPBoD8_375>{{Ref PCPBoD8|375}}</ref>
*Pleural plaques.
*Asbestosis.
*[[Lung carcinoma]].
*[[Malignant mesothelioma]].
 
 
Possible association with asbestos exposure:
*[[Gestational trophoblastic disease]].<ref name=pmid19900938>{{Cite journal  | last1 = Reid | first1 = A. | last2 = Heyworth | first2 = J. | last3 = de Klerk | first3 = N. | last4 = Musk | first4 = AW. | title = Asbestos exposure and gestational trophoblastic disease: a hypothesis. | journal = Cancer Epidemiol Biomarkers Prev | volume = 18 | issue = 11 | pages = 2895-8 | month = Nov | year = 2009 | doi = 10.1158/1055-9965.EPI-09-0731 | PMID = 19900938 }}</ref>
 
Diagnosis:
*Rests on morphology with special techniques (e.g. polarization)<ref>{{Cite journal  | last1 = Galateau-Salle | first1 = F. | title = [Anatomopathological tools for screening and medical surveillance of people exposed to asbestos]. | journal = Rev Mal Respir | volume = 16 | issue = 6 Pt 2 | pages = 1244-56 | month = Dec | year = 1999 | doi =  | PMID = 10897845 }}</ref> and includes tunneling [[electron microscopy]] (TEM),<ref name=pmid21479897>{{Cite journal  | last1 = Neumann | first1 = V. | last2 = Löseke | first2 = S. | last3 = Tannapfel | first3 = A. | title = Mesothelioma and analysis of tissue fiber content. | journal = Recent Results Cancer Res | volume = 189 | issue =  | pages = 79-95 | month =  | year = 2011 | doi = 10.1007/978-3-642-10862-4_6 | PMID = 21479897 }}</ref> as done at special centres.
**Tissue is typically digested prior to fibre counting.<ref name=pmid20196674>{{Cite journal  | last1 = Roggli | first1 = VL. | last2 = Gibbs | first2 = AR. | last3 = Attanoos | first3 = R. | last4 = Churg | first4 = A. | last5 = Popper | first5 = H. | last6 = Cagle | first6 = P. | last7 = Corrin | first7 = B. | last8 = Franks | first8 = TJ. | last9 = Galateau-Salle | first9 = F. | title = Pathology of asbestosis- An update of the diagnostic criteria: Report of the asbestosis committee of the college of american pathologists and pulmonary pathology society. | journal = Arch Pathol Lab Med | volume = 134 | issue = 3 | pages = 462-80 | month = Mar | year = 2010 | doi = 10.1043/1543-2165-134.3.462 | PMID = 20196674 }}</ref>
 
===Microscopic===
Features:<ref name=pmid20196674/>
#Interstitial fibrosis - similar to [[usual interstitial pneumonia]] (UIP).
#''Ferruginous bodies'' - '''key feature'''.
#*Segmented twirling baton with long slender fibre within.
 
====Images====
<gallery>
Image:Ferruginous_body.jpg | Ferruginous bodies. (WC)
Image:Asbestosis_high_mag.jpg | Asbestosis. (WC)
</gallery>


==Non-specific interstitial pneumonia==
==Non-specific interstitial pneumonia==
*Abbreviated ''NSIP''.
*Abbreviated ''NSIP''.
 
{{Main|Non-specific interstitial pneumonia}}
===General===
*Better prognosis than [[UIP]].
*Some radiologists and pathologists don't believe in this entity.
 
Associations:<ref name=Ref_WMSP92>{{Ref WMSP|92}}</ref>
*Connective tissue disease.
*[[Rheumatoid arthritis]].
 
===Gross/Radiology===
*No honeycombing.
*Fibrosis usually lower lung zone.
*Patchy ground glass.
 
===Microscopic===
Features:<ref name=Ref_WMSP92>{{Ref WMSP|92}}</ref>
*Diffuse fibrosis:
**Uniform fibrosis (unlike [[UIP]]).
**"Linear fibrosis" has a good prognosis - should be mentioned in the report.
***''Linear fibrosis'' = fibrosis that follows alveolar walls + no architectural distortion.
*+/-Lymphoid nodules - association with collagen vascular disease. (???)
*+/-Focal [[organizing pneumonia]].
 
Notes:
*Inflammation in NSIP usually more prominent than in UIP.
*No honeycombing - key difference between UIP and NSIP.
 
DDx:
*Collagen vascular disease.
*Drug reaction.
*[[Hypersensitivity pneumonitis]] (extrinic allergic alveolitis).
*[[Lymphocytic interstitial pneumonia]] (LIP) - much more inflammation.


==Organizing pneumonia==
==Organizing pneumonia==
===General===
{{Main|Organizing pneumonia}}
*Multiple causes, e.g. transplant rejection, infection.
 
Clinical diagnoses:<ref name=Ref_WMSP91>{{Ref WMSP|91}}</ref>
*[[Lung transplant pathology|Transplant rejection]].
*Cryptogenic organizing pneumonia (COP), [[AKA]] (idiopathic) bronchiolitis obliterans organizing pneumonia (BOOP).
**Should '''not''' be confused with ''[[constrictive bronchiolitis]]'' (AKA ''[[bronchiolitis obliterans]]'').
*[[Collagen vascular disease]].
*Toxic injury.
*Infection.
*Peri-tumor - in proximity to a space-occupying lesion (abscess, neoplasm).
 
Note:
*BOOP is used as a synonym for ''organizing pneumonia'' which has the long differential diagnosis above.<ref name=Ref_WMSP91>{{Ref WMSP|91}}</ref>
**Confusingly, it may be used to refer to the idiopathic form of organizing pneumonia, now generally known as ''cryptogenic organizing pneumonia'' (COP).
***In other words, strictly speaking, ''BOOP'' is '''not''' the same as ''COP''; idiopathic BOOP ''is'' COP.
 
===Microscopic===
Features:<ref name=Ref_Klatt110>{{Ref Klatt|110}}</ref>
*Distal airway disease -- airways plugged with organizing exudate ("[[Masson bodies]]").
**"Organized exudate" = fluffy light-staining paucicellular regions with stellate cells (fibroblasts & immature connective tissue).
*'''No''' hobnailing of pneumocytes.
**Type 2 pneumocytes hyperplasia is absent.
 
DDx:
*[[Diffuse alveolar damage]], proliferative phase - has type 2 pneumoncyte hyperplasia.
*[[Bronchiolitis obliterans]].
 
====Images====
<gallery>
Image:Masson_body_-_intermed_mag.jpg | Masson body - intermed. mag. (WC/Nephron)
Image:Masson_body_-_very_high_mag.jpg | Masson body - very high mag. (WC/Nephron)
</gallery>
www:
*[http://150.59.224.157/pathology/system/data/image_data/11338411170518.jpg Masson body (150.59.224.157)].<ref>URL: [http://150.59.224.157/pathology/index.php?first_category_id=2&second_category_id=20 http://150.59.224.157/pathology/index.php?first_category_id=2&second_category_id=20]. Accessed on: 4 August 2011.</ref>
*[http://casereports.bmj.com/content/2011/bcr.11.2010.3483.full BOOP (bmj.com)].
*[http://www.flickr.com/photos/pulmonary_pathology/4733384977/ Masson body (flickr.com)].


==Hypersensitivity pneumonitis==
==Hypersensitivity pneumonitis==
*AKA ''extrinsic allergic alveolitis''
*AKA ''extrinsic allergic alveolitis''
 
{{Main|Hypersensitivity pneumonitis}}
===General===
*Exposure to stuffs... e.g. moldy hay - ''Farmer's lung'', atypical mycobacteria - ''hot tub lung''.
*Upper lung predominant disease.
**Mnemonic ''FASSTEN'' - upper lung field: [[Farmer's lung]], [[Ankylosing spondylitis]], [[Sarcoidosis]], [[Silicosis]], [[Tuberculosis]] (miliary), [[Eosinophilic granuloma]], [[Neurofibromatosis]].
*An immune complex-mediated [[hypersensitivity]]<ref name=pmid8279154>{{Cite journal  | last1 = Kaltreider | first1 = HB. | title = Hypersensitivity pneumonitis. | journal = West J Med | volume = 159 | issue = 5 | pages = 570-8 | month = Nov | year = 1993 | doi =  | PMID = 8279154 | url = http://www.ncbi.nlm.nih.gov/pmc/articles/pmid/8279154/?tool=pubmed }}</ref> (Gell-Coombs classification type III).
**If chronic, may develop into a cell-mediated hypersensitivity (Gell-Coombs classification type IV).<ref>URL: [http://library.med.utah.edu/WebPath/EXAM/IMGQUIZ/pufrm.html http://library.med.utah.edu/WebPath/EXAM/IMGQUIZ/pufrm.html]. Accessed on: 4 December 2011.</ref>
 
===Microscopic===
Features:
* Lesions have centrilobular prominence - '''important feature'''. <ref name=pmid16061708/>
** Allergens enter lung through airway which has a centrilobular location.
* [[Granulomata]] (not typically seen in UIP) - '''important feature'''.<ref name=pmid16061708>{{Cite journal  | last1 = Ohtani | first1 = Y. | last2 = Saiki | first2 = S. | last3 = Kitaichi | first3 = M. | last4 = Usui | first4 = Y. | last5 = Inase | first5 = N. | last6 = Costabel | first6 = U. | last7 = Yoshizawa | first7 = Y. | title = Chronic bird fancier's lung: histopathological and clinical correlation. An application of the 2002 ATS/ERS consensus classification of the idiopathic interstitial pneumonias. | journal = Thorax | volume = 60 | issue = 8 | pages = 665-71 | month = Aug | year = 2005 | doi = 10.1136/thx.2004.027326 | PMID = 16061708 }}</ref>
* Chronic interstitial inflammation consisting primarily of lymphocytes.
* Interstitial fibrosis.
* Air space involvement (alveolitis).
 
DDx:
*[[Usual interstitial pneumonia]].
 
====Images====
<gallery>
Image:Hypersensitivity_pneumonitis_low_mag.jpg | Hypersensitivity pneumonitis - low mag. (WC/Nephron)
Image:Hypersensitivity_pneumonitis_intermed_mag.jpg | Hypersensitivity pneumonitis - intermed. mag. (WC/Nephron)
Image:Hypersensitivity_pneumonitis_high_mag.jpg | Hypersensitivity pneumonitis - high mag. (WC/Nephron)
</gallery>


==Lymphocytic interstitial pneumonia==
==Lymphocytic interstitial pneumonia==
*Often abbreviated '''''LIP'''''.
*Often abbreviated '''''LIP'''''.
===General===
{{Main|Lymphocytic interstitial pneumonia}}
*Associated with autoimmune disorders ([[rheumatoid arthritis]], [[pernicious anemia]], [[Sjoegren syndrome]])<ref>URL: [http://emedicine.medscape.com/article/299643-overview http://emedicine.medscape.com/article/299643-overview]. Accessed on: 2 June 2010.</ref> and immunodeficiency.<ref name=pmid16088689>{{cite journal |author=Nicholson AG |title=Lymphocytic interstitial pneumonia and other lymphoproliferative disorders in the lung |journal=Semin Respir Crit Care Med |volume=22 |issue=4 |pages=409–22 |year=2001 |month=August |pmid=16088689 |doi=10.1055/s-2001-17384 |url=}}</ref>
*Associated with viral infections ([[HIV]], EBV, human T-cell leukemia virus (HTLV) type 1).
**Considered an AIDS-defining diagnosis.<ref>{{Cite journal  | last1 = Turner | first1 = BJ. | last2 = Eppes | first2 = S. | last3 = McKee | first3 = LJ. | last4 = Cosler | first4 = L. | last5 = Markson | first5 = LE. | title = A population-based comparison of the clinical course of children and adults with AIDS. | journal = AIDS | volume = 9 | issue = 1 | pages = 65-72 | month = Jan | year = 1995 | doi =  | PMID = 7893443 }}</ref>
 
===Gross===
*Location: basilar predominance.
*Increased interstitial markings.
 
===Microscopic===
Features:<ref>URL: [http://emedicine.medscape.com/article/299643-diagnosis http://emedicine.medscape.com/article/299643-diagnosis]. Accessed on: 2 June 2010.</ref>
*Small mature lymphocytes (usually B cells)<ref name=afip_vol2_265>AFIP atlas of nontumour pathology. 2002. Vo. 2. P.265. ISBN 1-881041-79-4.</ref> in the interstitium of the lung.
*Plasma cells.
*+/-Lymphoid follicles.
 
Negatives:
*No [[vasculitis]].
*No [[necrosis]].
 
Images:
*[http://www.scielo.br/img/revistas/jbpneu/v34n2/en_a02fig01.jpg LIP (scielo.br)].
*[http://path.upmc.edu/cases/case176/micro.html LIP (upmc.edu)].
 
DDx:
*[[Lymphoma]].
*Follicular bronchitis/bronchiolitis.
*Nodular lymphoid hyperplasia.
**This is determined in part by radiology; it has nodules radiographically.
 
===Stains===
To exclude infection:<ref>URL: [http://path.upmc.edu/cases/case176/dx.html http://path.upmc.edu/cases/case176/dx.html]. Accessed on: 8 January 2012.</ref>
*[[GMS stain]] -ve.
*[[Ziehl-Neelsen stain]] -ve.
 
===IHC===
*May be done to exclude lymphoma.


==Respiratory bronchiolitis-interstitial lung disease==
==Respiratory bronchiolitis-interstitial lung disease==
*Abbreviated ''RB-ILD'' or ''RBILD''.
*Abbreviated ''RB-ILD'' or ''RBILD''.
*[[AKA]] ''respiratory bronchiolitis-associated interstitial lung disease''.
*[[AKA]] ''respiratory bronchiolitis-associated interstitial lung disease''.
 
{{Main|Respiratory bronchiolitis-interstitial lung disease}}
===General===
*May be an early version of ''[[DIP]]''.
*Associated with smoking.
 
===Microscopic===
Features:<ref name=Ref_PPP197-8>{{Ref PPP|197-8}}</ref>
*Brown pigmented airspace macrophages - ''smoker's macrophages'' - '''key feature'''.
*Inflammation of the terminal bronchioles.
 
Note:
*The histologic features of RBILD may be present peri-tumoural.
 
DDx:
*[[Desquamative interstitial pneumonia]].
 
Image:
*[http://www.nature.com/modpathol/journal/v19/n11/fig_tab/3800671f2.html RB-ILD (nature.com)].


==Desquamative interstitial pneumonia==
==Desquamative interstitial pneumonia==
*Abbreviated ''DIP''.
*Abbreviated ''DIP''.
===General===
{{Main|Desquamative interstitial pneumonia}}
*Thought to be advanced ''[[RBILD]]''.
*Strong association with smoking.<ref name=Ref_WMSP93>{{Ref WMSP|93}}</ref>
**Treatment: stop smoking.
 
===Microscopic===
Features:
*Abundant brown pigmented airspace macrophages - ''smoker's macrophages'' - '''key feature'''.
*Architecture preserved; "linear fibrosis".
 
Notes:
*Some fields of view may be indistinguishable from [[RBILD]].
 
DDx:
*Amiodarone toxicity.
*Fibrotic [[NSIP]].
 
Images:
*[http://pathhsw5m54.ucsf.edu/case27/dip27.html DIP (ucsf.edu)].
 
===Stains===
*Macrophages PAS +ve.


=See also=
=See also=
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