36 Pathology 4: Interstitial Lung Diseases Flashcards
1
Q
Pulmonary architecture:
Lung compartments
- Airspaces
- Interstitium
- Bronchovascular bundles
- Airways
- Pleura
A
- Airspaces
- Distal airspace
- Mostly the alveoli
- Interstitium
- Mostly alveolar septa an dinterlobular septa
- Bronchovascular bundles
- Vessels
- Airways
- Large airways: bronchi
- Small airways: bronchioles
- Pleura
- Anatomically not part of the lung, but can be involved in lung disease
2
Q
Pulmonary architecture
- The pulmonary interstitium
- In the healthy lung, alveolar septa are…
- The basement membranes of epithelium and vascular endothelium
- The interstitium is the primary site of…
A
- The pulmonary interstitium
- Forms a three-dimensional scaffold that imparts structural integrity to the lung
- In the healthy lung, alveolar septa are…
- Very delicate
- Composed of a single layer of flattened pneumocytes, a capillary, and a very small amount of extracellular matrix
- The basement membranes of epithelium and vascular endothelium
- In thin portions of the alveolar septum are fused (allows easy gas diffusion)
- In the thicker portions are separated by an interstitial space containing some extracellular matrix, fibroblasts-like interstitial cells and some smooth muscle cells
- The interstitium is the primary site of…
- Injury in the interstitial lung diseases
3
Q
Pulmonary architecture:
The main supply routes of the lung
- Pulmonary arteries
- Airways
- Bronchial arteries
- Pulmonary veins
- Lymphatics
A
- Pulmonary arteries
- Run in the bronchovascular bundles in the center of the lung lobules (centrilobular)
- Airways
- Run in the bronchovascular bundles in the center of the lobules (centrilobular)
- Bronchial arteries
- Run with the airways they supply (centrilobular)
- Pulmonary veins
- Form in the lobules and then run to the nearest interlobular septum, and from there to the nearest interlobar septum or the pleural surface (septal)
- Lymphatics
- Follow both the routes of veins and arteries (centrilobular and septal)
4
Q
Pulmonary architecture:
Two other noteworthy properties of the lungs
- Surface area
- Exposure to blood
A
- The lungs’ large surface area
- Forms one of the largest interfaces between the human organism and the environment
- The other two being skin and the gastrointestinal tract
- However, this interface is the one most difficult to protect from noxious stimuli (and often even voluntarily exposed to noxious stimuli)
- Hence, lung disease is very common, and probably not infrequently subclinical
- Forms one of the largest interfaces between the human organism and the environment
- The lungs are the only organs that encounter the entire cardiac output of blood
- They are theoretically exposed to hematogenous factors derived from all other tissues in the body
- It is therefore not surprising that the lungs are often involved in disease that occur elsewhere in the body
- Ranging from metastatic disease in cancer patients to lung fibrosis in patient with systemic connective tissue diseases such as rheumatoid arthritis
5
Q
Pulmonary response to injury
- Three most important reaction patterns to injury
- Airspace organization
- Hallmark feature of interstitial pneumonias
- Consequence of inflammation
- Whenvever airspace organization is the predominant findings,…
- Since the lung compartments are intimately associated, one often sees…
A
- Three most important reaction patterns to injury
- Airspace organization
- Inflammatory infiltrates
- Fibrosis
- Airspace organization
- Involves primarily the airspaces
- Classical example: organizing pneumonia
- Hallmark feature of interstitial pneumonias
- Inflammatory infiltrates which primarily involve the interstitium
- Consequence of inflammation
- Fibrosis
- The degree of fibrosis, or scarring, depends on…
- The degree and duration of the inflammatory process
- The extent of tissue destruction by the inflammatory process
- Whenvever airspace organization is the predominant findings,…
- The disease is usually not considered an “interstitial lung disease”
- Since the lung compartments are intimately associated, one often sees…
- Some “airspace” disease in “interstitial” lung disease
- Some “interstitial” inflammation in “airspace” disease
6
Q
Pulmonary response to injury
- The earliest common manifestation of most of the interstitial diseases
- The initial stimuli for this damage
- The accumulation of inflammatory and immune effector cells within the alveolar walls and spaces
- Neutrophil recruitment can be caused by…
- Alveolar macrophages
- In diseases such as sarcoidosis, cell-mediated immune reactions result in…
- What’s responsible for the slowly progressive pulmonary fibrosis
- The alveolar macrophage plays a central role in the development of…
- Loss of homeostatic matrix regulation with concomitant alterations in synthesis and degradation results in…
A
- The earliest common manifestation of most of the interstitial diseases
- Damage to the alveolar structure
- The initial stimuli for this damage
- Heterogeneous
- Some of these stimuli, such as oxygen-derived free radicals and some chemicals, are directly toxic to endothelial cells, epithelial cells, or both
- The accumulation of inflammatory and immune effector cells within the alveolar walls and spaces
- Distorts the normal alveolar structures
- The inflammatory cells release mediators that injure parenchymal cells and stimulate fibrosis
- Neutrophil recruitment can be caused by…
- Complement activation in some disorders
- Alveolar macrophages
- Increase in number in all interstitial diseases
- Release chemotactic factors for neutrophils (e.g., IL-8, leukotriene B4)
- In diseases such as sarcoidosis, cell-mediated immune reactions result in…
- The accumulation of monocytes and T lymphocytes and in the formation of granulomas
- What’s responsible for the slowly progressive pulmonary fibrosis
- The interactions among lymphocytes and macrophages
- The release of lymphokines and monokines
- The alveolar macrophage plays a central role in the development of…
- Fibrosis
- Not only the infiltrating inflammatory cells, but also local (resident) cells become stimulated and release soluble factors that promote fibroblast activation, proliferation, and matrix production
- Loss of homeostatic matrix regulation with concomitant alterations in synthesis and degradation results in…
- The disproportionate deposition of lung connective tissue
7
Q
Classification of the interstitial lung diseases
- Interstitial lung diseases
- General
- Affect…
- The result of the inflammation and fibrosis
- In the late stages of pulmonary fibrosis,…
- In most of the diseases, the process is…
- The radiographic and gross anatomic diagnosis
- Classification of interstitial lung diseases
A
- Interstitial lung diseases
- A heterogeneous group of non-neoplastic disorders resulting from damage predominantly to the pulmonary interstitium by varying patterns of inflammation and fibrosis
- Frequently affect not only the interstitium, but also the airspaces, airways, and pulmonary vessels
- The result of the inflammation and fibrosis is a marked decrease in pulmonary compliance, significant reduction in oxygen exchange (diffusing capacity), pulmonary hypertension, right heart dilatation and failure (cor pulmonale), and death
- In the late stages of pulmonary fibrosis,…
- The lung is remodeled into extensive scar tissue
- In most of the diseases, the process is…
- Uneven throughout the pulmonary parenchyma, with some less-involved airways (especially respiratory bronchioles) stretched wide by scar contraction
- The radiographic and gross anatomic diagnosis
- “Honeycomb lung” or “honeycomb change”
- Classification of interstitial lung diseases
- Not every interstitial lung disease is idiopathic, but many (nonidiopathic) interstitial lung diseases are commonly described using the same terminology
8
Q
Classification of the interstitial lung diseases
- Etiological classifications
- Unknown etiology diseases
- Inorganic dust diseases
- Organic dust diseases
- Drugs and radiation diseases
A
- Etiological classifications
- Infection
- Inorganic dust exposure
- Organic dust exposure
- Idiopathic
- Drug-induced
- Unknown etiology diseases
- Idiopathic interstitial pneumonia (IP)
- Usual interstitial pneumonia (UIP)
- Non-specific IP (NSIP)
- Desquamative IP (DIP)
- Lymphoid IP (LIP)
- Cryptogenic organizing pneumonia (COP)
- Acute interstitial pneumonia (AIP)
- Respiratory bronchiolitis-associated interstitial lung disease (RB-ILD)
- Systemic disease associated
- Includes connective tissue/autoimmune diseases
- Many of the entities seen in this setting have radiographic and histologic findings resembling or identical to the idiopathic IPs listed above
- Sarcoidosis
- Pulmonary Langerhans cell histiocytosis
- Lymphangioleiomyomatosis
- Chronic eosinophilic pneumonia
- Idiopathic interstitial pneumonia (IP)
- Inorganic dust diseases
- Pneumoconioses
- Coal workers pneumoconiosis
- Asbestosis
- Silicosis
- Many others
- Pneumoconioses
- Organic dust diseases
- Hypersensitivity pneumonitis
- Drugs and radiation diseases
- Drugs and radiation-induced diseases
9
Q
Usual interstitial pneumonia and idiopathic pulmonary fibrosis
- Usual interstitial pneumonia (UIP)
- Idiopathic pulmonary fibrosis (IPF)
- IPF vs. UIP
A
- Usual interstitial pneumonia (UIP)
- A diffuse fibrosing lung disease that shows the histologic features “usually” seen in this entity
- Any disease that histologically looks like UIP
- Idiopathic pulmonary fibrosis (IPF)
- A chronic fibrosing lung disease in older people with no apparent cause
- Histologic findings are those of UIP
- IPF vs. UIP
- IPF is a clinical term
- UIP is a patholgy term
- Every IPF has the histopathologic features of UIP, but not every UIP is IPF
- Ex. UIP can be the histologic findings in lung involvement by connective tissue disease or lung disease related to asbestos exposure (asbestosis), organic dust exposure (hypersensitivity pneumonitis) or drug toxicities
10
Q
Usual interstitial pneumonia and idiopathic pulmonary fibrosis
- IPF is characterized by…
- Prognosis
A
- IPF is characterized by…
- Marked interstitial fibrosis
- An insidious onset with slow but inexorable progression
- A poor prognosis with most patients dying of their disease
- Prognosis
- Poor
- Median survival without lung transplant is between 3 and 5 years
- Median survival of a lung transplant recipient is also only about 5 years
11
Q
Usual interstitial pneumonia and idiopathic pulmonary fibrosis
- The key histologic features of the UIP pattern
- Fibrosis
- Fibroblastic focus/foci
- Main constituents of scar tissue or fibrosis
- Diagnostic feature of UIP
A
- The key histologic features of the UIP pattern
- Architectural distortion
- Fibrosis with honeycomb change
- Fibroblastic foci
- Patchy distribution
- Fibrosis
- Starts in the periphery of a lung lobule (the small secondary lung lobule, not the whole lobe)
- Advances to the center of the lobule
- Fibroblastic focus/foci
- At the interface between fibrosis and uninvolved lung
- An area in which the fibrosis is actively happening and advancing
- Have the appearance of an “immature” fibrosis
- They look rather loose and do not contain many collagen fibers
- Main constituents of scar tissue or fibrosis
- Collagen fibers
- Stain red with the pathologists’ routine Hematoxylin & Eosin stain
- Fibrotic biopsies overall look very “red” or “pink” under the microscope
- Diagnostic feature of UIP
- Spared areas of lung that looks rather normal (“usual”)
12
Q
Usual interstitial pneumonia and idiopathic pulmonary fibrosis
- Geographic heterogeneity
- Temporal heterogeneity
- To make the diagnosis of UIP ona lung biopsy, the pathologist needs to see…
- Interdisciplinary discussion among pulmonologist, radiologist and pathologist
- What causes IPF
A
- Geographic heterogeneity: coexistence of…
- Remodeled/scarred lung
- Near normal, spared
- Temporal heterogeneity: coexistence of…
- Mature scar tissue with dense collagen
- Immature fibrosis characterized by fibroblastic foci
- To make the diagnosis of UIP ona lung biopsy, the pathologist needs to see…
- Fibrosis of the lung with distortion of lung architecture (often accompanied by honeycomb change)
- Geographic heterogeneity
- Temporal heterogeneity
- Interdisciplinary discussion among pulmonologist, radiologist and pathologist
- Usually the best way to place patients into a diagnostic category if the diagnosis is unclear
- What causes IPF
- Unknown (hence “idiopathic”)
13
Q
Usual interstitial pneumonia and idiopathic pulmonary fibrosis
- Risk factors associated with IPF
- Some patients with familial disease have been found to carry certain mutations in…
- Some of these mutations have also been identified in individuals with…
- It is unclear whether…
- What induces a fibrotic environment
- The fibroblastic focus may represent…
- While similar injuries may occur in people without IPF, IPF patients may…
A
- Risk factors associated with IPF
- Cigarette smoking
- Environmental pollutants
- Chronic microaspiration
- Some patients with familial disease have been found to carry certain mutations in…
- Surfactant proteins
- Gel-forming mucin
- Telomerase
- Some of these mutations have also been identified in individuals with…
- Sporadic IPF, suggesting there may be a genetic predisposition in some patients
- It is unclear whether…
- Inflammation is the primary problem in this disease that in the long run results in fibrosis
- The fibrosis occurs in the absence of much inflammation due to aberrant epithelial cell and fibroblast responses to some nonspecific lung injury
- What induces a fibrotic environment
- Multiple microinjuries to alveolar epithelial cells (for example a “cracking” open of the alveolar lining caused by a stretch injury)
- Growth factors secreted by the injured epithelial cells activate and recruit fibroblasts
- The fibroblastic focus may represent…
- Repair at the initial site of such injury
- While similar injuries may occur in people without IPF, IPF patients may…
- Lack the ability to limit the repair and move on to excessive scar formation
involving the whole lung
- Lack the ability to limit the repair and move on to excessive scar formation
14
Q
Lung involvement by sarcoidosis
- Sarcoidosis
- Macroscopically,…
- Histological hallmarks
- Histiocytes
- Epitheliod histiocytes
A
- Sarcoidosis
- A systemic disease of unknown cause characterized by non-necrotizing granulomatous inflammation in various tissues and organs
- The lung is one of the organs commonly involved in sarcoidosis (in about 90%), often together with the mediastinal lymph nodes
- Macroscopically,…
- There are no focal lesions
- At times, the coalescence of granulomas produces small nodules
- Histological hallmarks
- Classic non-necrotizing granulomas
- Composed of an aggregate of tightly clustered epithelioid histiocytes with
multinucleated giant cells- Epithelioid histiocytes: histiocytes that look similar to an epithelial cell
- Histiocytes
- Macrophages that have a permanent position in a tissue
- Macrophage: a monocyte once it leaves the blood stream
- Derived from the monocyte system, so their progenitors are in the bone marrow
- Primary goal: clean up
- Macrophages that have a permanent position in a tissue
- Epitheliod histiocytes
- Histiocytes that look similar to an epithelial cell
- Normal macrophages/histiocytes transform under IL-1 and TNF-α influence into these bigger, more round macrophages with abundant cytoplasm
- Sometimes coalesce and form multinucleated giant cells
15
Q
Lung involvement by sarcoidosis
- Scar formation
- The granulomas in sarcoidosis
- Two additional microscopic features of the granulomas that are sometimes seen in sarcoidosis
A
- Scar formation
- With chronicity dense fibrous scars surround the granulomas of sarcoidosis
- This scar formation can progress (and the granulomatous inflammation subside) so that in late stages of sarcoidosis only scars are left behind, and one may be lucky to find a single giant cell
- The granulomas in sarcoidosis
- Consistently arranged along lymphovascular routes in the lung
- Main locations: lymphovascular routes are along the bronchovascular bundles and along the septa and pleura
- Occasionally find granulomas in alveolar septa as well
- The relative frequency of granulomas in the bronchial submucosa accounts for the high diagnostic yield of bronchoscopic biopsies
- Two additional microscopic features of the granulomas that are sometimes seen in sarcoidosis
- Neither one of them are pathognomonic of sarcoidosis
- “Schaumann bodies” are laminated concretions composed of calcium and proteins
- “Asteroid bodies” are stellate inclusions containing degraded cytoskeletal protein enclosed within multinucleated giant cells
16
Q
Lung involvement by sarcoidosis
- Histopathologic features of sarcoidosis
- Possible causes of sarcoidosis
A
- Histopathologic features of sarcoidosis
- Granulomatous inflammation with well formed non-necrotizing granulomas in
- Lymphangitic distribution
- Possible causes of sarcoidosis
- Exposure to certain microorganisms (especially mycobacteria and propionibacteria)
- Certain dusts (Beryllium exposure results in a histologically similar lung disease)
- Altered cytokine and T cell responses
17
Q
Silicosis
- General
- Frequency
- Presentation
- Risk factors
- Acute silicosis
A
- General
- A lung disease caused by inhalation of crystalline silicon dioxide (silica)
- Frequency
- The most prevalent chronic occupational disease in the world
- Presentation
- Usually presents after decades of exposure as a slowly progressing, nodular, fibrosing pneumoconiosis
- Risk factors
- Workers in a large number of occupations are at risk, especially sandblasters and many mine workers
- Less commonly, heavy exposure over months to a few years can result in acute silicosis
- Acute silicosis
- A lesion characterized by the generalized accumulation of a lipoproteinaceous material within alveoli
- Histologically indistinguishable from pulmonary alveolar Proteinosis
18
Q
Silicosis
- Forms
- Process
- Animals exposed to silica demonstrate…
A
- Forms
- Both crystalline and amorphous forms
- Crystalline forms (including quartz, crystobalite, and tridymite) are much more fibrogenic
- Reveals the importance of the physical form and surface properties in pathogenesis
- Of these, quartz is most commonly implicated in silicosis
- Process
- After inhalation, the particles interact with epithelial cells and macrophages
- Although lung macrophages that ingest the silica particles may ultimately succumb to its toxic effects, silica causes activation and release of mediators by viable macrophages
- Such mediators include IL-1, tumor necrosis factor (TNF), fibronectin, lipid
mediators, oxygen-derived free radicals, and fibrogenic cytokines
- Such mediators include IL-1, tumor necrosis factor (TNF), fibronectin, lipid
- Animals exposed to silica demonstrate…
- A steady recruitment of macrophages and lymphocytes to the alveoli and interstitium, which further amplify the pathologic process
- Anti-TNF monoclonal antibodies can block lung collagen accumulation in mice that are given silica intratracheally
- TNF seems to be an important mediator in inflammatory diseases
19
Q
Silicosis
- Histopathologically, silicosis is characterized by discrete nodules in the upper zones of the lungs
- Early vs. later stages
- Other findings
- Eggshell calcification
- Progressive massive fibrosis (PMF)
- Often, patients exposed to silica (“free” silicon dioxide = SiO2) are also exposed to…
- Asbestos
- Main points about silicosis
A
- Histopathologically, silicosis is characterized by discrete nodules in the upper zones of the lungs
- Early vs. later stages
- In early stages these nodules are tiny and barely palpable
- As the disease progresses, these nodules may coalesce into hard, collagenous scars
- Other findings
- Some nodules may undergo central degeneration and cavitation
- Acid-fast bacteria in those nodules may be due to superimposed tuberculosis
- Fibrotic lesions may also occur in the hilar lymph nodes and pleura
- Eggshell calcification
- Sometimes, thin sheets of calcification occur in the lymph nodes
- These are seen radiographically as calcium surrounding a zone lacking calcification
- Early vs. later stages
- Progressive massive fibrosis (PMF)
- If the disease continues to progress, expansion and coalescence of lesions produce PMF
- Examination of silicotic nodules by polarization microscopy reveals very faint birefringent silica particles
- Often, patients exposed to silica (“free” silicon dioxide = SiO2) are also exposed to…
- Silicates (“combined” silicon dioxide = SiO2 that is bound to other minerals, for example magnesium or aluminum)
- When one views a silicosis case under the microscope, one sees not only the dim silica particles but also the slightly larger and much brighter silicate crystals.
- Asbestos
- A silicate (there are many different asbestos silicates) with striking health effects
- Main points about silicosis
- Exposure to silica (silicon dioxide = SiO2)
- Upper lobe predominant single or confluent nodules
20
Q
Coal worker pneumoconiosis (CWP)
- Coal worker pneumoconiosis
- The spectrum of lung findings in coal workers
- Like silicosis, CWP preferentially involves…
- Excluding lung cancer
- Things to remember about CWP
A
- Coal worker pneumoconiosis
- A lung disease caused by the inhalation of coal dust
- The spectrum of lung findings in coal workers
- Asymptomatic anthracosis
- Simple CWP with little to no pulmonary dysfunction
- Complicated CWP, or progressive massive fibrosis (PMF), in which lung function is compromised
- Like silicosis, CWP preferentially involves…
- The upper lung zones
- Excluding lung cancer
- Often they are smokers
- Even if biopsy of one nodule shows only fibrosis, one can never exclude with certainty that another nodule represents lung cancer
- Things to remember about CWP
- The difference between simple CWP and complicated CWP (progressive massive fibrosis) is the size of the conglomerate fibrotic masses
- Upper lung zone predominant disease
21
Q
Coal worker pneumoconiosis (CWP)
- Histopathologically, the most innocuous coal-induced pulmonary lesion in CWP
- Process
- Fibrosis at this stage
- Simple CWP
- Complicated CWP (or progressive massive fibrosis, PMF)
- People in the mines are often not only exposed to pure coal dust but also to…
A
- Histopathologically, the most innocuous coal-induced pulmonary lesion in CWP
- Coal dust macules
- Consists of carbon-laden macrophages embedded in a delicate network of collagen fibers
- Process
- Inhaled carbon pigment is engulfed by alveolar or interstitial macrophages, which then accumulate in the connective tissue along the lymphatics, including the pleural lymphatics
- Fibrosis at this stage
- Minimal
- Simple CWP
- Coal macules (1 to 2 mm in diameter) and somewhat larger coal dust nodules
- Located primarily adjacent to respiratory bronchioles, the site of initial dust
accumulation - Coal macules do not grow after coal dust exposure ceases, though patients will cough up black dust for years afterwards
- Complicated CWP (or progressive massive fibrosis, PMF)
- Occurs on a background of simple CWP
- Generally requires many years to develop
- Defined by the size of the nodules (> 2 cm)
- There are usually multiple nodules
- Microscopically, the lesions consist of dense collagen and carbon pigment
- Sometimes the center of a big nodule is necrotic, resulting most likely from local ischemia
- People in the mines are often not only exposed to pure coal dust but also to…
- Silica or silicates
- Therefore, it is common to see silicotic nodules and birefringent crystals in patients with CWP
22
Q
Asbestosis
- Asbestosis
- Asbestos
- Occupational exposure to asbestos is linked to…
- What dictates whether asbestos causes disease
- Two distinct geometric forms of asbestos
- Asbestos fibers that remain in the lung
- Amphiboles
A
- Asbestosis
- A lung disease caused by the inhalation of asbestos
- Asbestos
- A family of fibrous minerals, hydrated silicates of sodium, iron, calcium, and
magnesium
- A family of fibrous minerals, hydrated silicates of sodium, iron, calcium, and
- Occupational exposure to asbestos is linked to…
- Localized fibrous plaques or, rarely, diffuse pleural fibrosis (benign)
- Pleural effusions (benign)
- Parenchymal interstitial fibrosis (asbestosis) (benign)
- Lung carcinoma (malignant)
- Mesothelioma (malignant)
- Laryngeal and other extrapulmonary neoplasms, including colon carcinomas, and perhaps malignant lymphomas (malignant)
- What dictates whether asbestos causes disease
- Fiber burden, size, shape, and solubility of the different forms of asbestos
- Two distinct geometric forms of asbestos
- Serpentine (curly and flexible fibers)
- Amphibole (straight, stiff, and brittle fibers)
- Asbestos fibers that remain in the lung
- Long (mean length about 35 micrometer)
- Slender (around 2 to 5 micrometer)
- They can…
- Cause local fibrosis just like the other silicates
- Get carried through lymphatics to the pleura where we think they cause mesothelioma
- Amphiboles
- Less prevalent
- The most fibrogenic and pathogenic
23
Q
Asbestosis
- The occurrence of asbestosis, like the other pneumoconioses, depends on…
- The initial injury occurs…
- Macrophages
- Chronic deposition of fibers and persistent release of mediators eventually lead to…
- In contrast to other inorganic dusts, asbestos can also act as…
- Some of the oncogenic effects of asbestos are mediated by…
- For example, the adsorption of carcinogens in tobacco smoke onto asbestos fibers may well be important in the remarkable synergy between…
A
- The occurrence of asbestosis, like the other pneumoconioses, depends on…
- The interaction of inhaled fibers with lung macrophages and other parenchymal cells.
- The initial injury occurs…
- At bifurcations of small airways and ducts, where the asbestos fibers land and penetrate
- Macrophages
- Both alveolar and interstitial
- Attempt to ingest and clear the fibers
- Are activated to release chemotactic factors and fibrogenic mediators that amplify the response
- Chronic deposition of fibers and persistent release of mediators eventually lead to…
- Generalized interstitial pulmonary inflammation and interstitial fibrosis
- In contrast to other inorganic dusts, asbestos can also act as…
- A tumor promoter
- Some of the oncogenic effects of asbestos are mediated by…
- Reactive free radicals generated by asbestos fibers
- Toxic chemicals can adsorb onto the asbestos fibers contributing to the oncogenicity of the fibers
- For example, the adsorption of carcinogens in tobacco smoke onto asbestos fibers may well be important in the remarkable synergy between…
- Tobacco smoking and the development of lung carcinoma in asbestos workers
24
Q
Asbestosis
- Histopathologically, asbestosis is marked by…
- Asbestos bodies
- Ferruginous bodies
- Fibrosis in asbestosis
A
- Histopathologically, asbestosis is marked by…
- Diffuse pulmonary interstitial fibrosis, which is sometimes indistinguishable from diffuse interstitial fibrosis resulting from other causes, except for the presence of asbestos bodies
- Asbestos bodies
- Appear as golden brown, fusiform or beaded rods with a translucent center
- Consist of asbestos fibers coated with an iron-containing proteinaceous material
- Arise when macrophages attempt to phagocytose asbestos fibers
- The iron is presumably derived from phagocyte ferritin
- Ferruginous bodies
- Other inorganic particulates may become coated with similar iron protein complexes
- Sometimes one cannot tell for sure whether a body is an asbestos body or not
- Fibrosis in asbestosis
- Fibrosis around respiratory bronchioles and alveolar ducts and extends to involve adjacent alveolar sacs and alveoli
- The fibrous tissue distorts the native architecture, creating enlarged airspaces enclosed within thick fibrous walls
- Eventually, the affected regions become honeycombed
25
Q
Asbestosis
- Asbestosis vs. UIP
- In contrast to CWP and silicosis, asbestosis…
- Pulmonary hypertension
- Pleural plaques
- Things to remember about asbestosis
A
- Asbestosis vs. UIP
- The pattern of fibrosis is similar to that seen in UIP, with fibroblastic foci and varying degrees of fibrosis
- The only difference is the presence of asbestos bodies
- In contrast to CWP and silicosis, asbestosis…
- Begins in the lower lobes and subpleurally (just like idiopathic UIP = IPF)
- The middle and upper lobes of the lungs become affected as fibrosis progresses
- Pulmonary hypertension
- Caused by the scarring trapping and narrowing pulmonary arteries and arterioles
- Pleural plaques
- The most common manifestation of asbestos exposure
- Well-circumscribed plaques of dense collagen often containing calcium
- Usually do not contain asbestos bodies
- If you see plaques in a patient, there is a very high probability that the patient
was exposed to asbestos - But the presence of plaques does not mean that the patient is at higher risk for mesothelioma or lung cancer than another exposed patient without plaques
- Things to remember about asbestosis
- Amphibole asbestos fibers are the most dangerous
- Asbestosis is lower lobe predominant
- Asbestosis can look like UIP/IPF, exposure history and asbestos body counts on slides are important
