Pleural Pathology Flashcards
What are the different layers of the pleura?
the visceral pleura lines the lungs
the parietal pleura is the outer layer of pleura
there is a pleural cavity between these 2 layers
What is the microanatomy of the pleural layers like?
- both layers of pleura (parietal / visceral) consist of connective tissue and mesothelium
What is the normal mesothelium of the pleura like?
What do they secrete and what is the purpose of this?
a single layer of mesothelial cells lines the pleural cavity
they secrete hyaluronic acid rich pleural fluid
this lubricates the movement of the visceral and parietal pleura against each other during respiration
What are the 3 categories of pleural pathology?
- inflammation - pleurisy or pleuritis
- fibrosis
- neoplasia
What are the causes of pleural inflammation?
primary inflammatory diseases:
- collagen vascular diseases such as SLE & rheumatoid arthritis
infections:
- usually secondary to pneumonia or pulmonary tuberculosis
- viral - primary coxsackie B infection (Bornholm disease)
pulmonary infarction:
- usually secondary to pulmonary arterial thromboembolus
emphysema:
- secondary to ruptured bullae
neoplasms:
- primary or secondary pleural neoplasms
therapeutic:
- pleurodesis usually with talc to treat recurrent pleural effusions or pneumothoraxes
iatrogenic:
- radiotherapy to the thorax
- immune reactions to drugs
If there is no associated pleural effusion, how is pleural inflammation diagnosed?
- pleuritic chest pain - a sharp localised pain exacerbated by breathing
- auscultation of a pleural rub during breathing
What does it usually suggest if there is pleural inflammation and associated pleural effusion?
this describes the presence of excess fluid in the pleural cavity
it usually suggests pleural fibrosis
what are the different types of pleural fibrosis?
- it is usually secondary to pleural inflammation
- unilateral or bilateral
- localised or diffuse
- asbestos associated pleural fibrosis
- parietal pleural fibrous plaques
- diffuse pleural fibrosis
What are the effects of pleural fibrosis?
widespread thick fibrosis can prevent normal lung expansion
compression of the lung during respiration can cause breathlessness
fibrous adhesions can wholly ot partially obliterate the pleural cavity
How can the effects of pleural fibrosis be alleviated?
pleural decortication
this is the removal of fibrous tissue
this improves lung expansion and compression of the lung during respiration
What are parietal pleural fibrous plaques associated with?
What are the symptoms?
associated with low level asbestos dust exposure
they consist of dense poorly cellular collagen and may be visible on chest X-rays
they are asymptomatic
What is diffuse pleural fibrosis associated with?
What is it and what can it cause?
associated with high levels of asbestos dust exposure
it is usually bilateral and consists of dense cellular collagen not extending into interlobal fissures
this prevents normal expansion and compression of the lung during breathing, causing breathlessness
What are the different pathological liquids that may be in the pleural cavities?
- serous fluid - pleural effusion
- pus - empyema or pyothorax
- usually secondary to pneumonia
- blood - haemothorax
- usually traumatic or a ruptured thoracic aortic aneurysm
- bile - chylothorax
- usually traumatic
What is it called if there is air in the pleural cavity?
pneumothorax
What are the 2 different types of pleural effusions?
transudates and exudates
What is the composition of and characteristics of a transudate pleural effusion?
- low capillary oncotic (colloid osmotic) pressure and/or high capillary hydrostatic pressure
- intact capillaries retain semipermeability
- low protein (<2.5 g/dL) & low lactate dehydrogenase
What is the composition of and the characteristics of an exudate pleural effusion?
- normal capillary oncotic pressure and normal vascular hydrostatic pressure
- pathological capillaries lose their semipermeability
- high protein (>2.9 g/dL) and high lactate dehydrogenase
What are the causes of a transudate pleural effusion?
- high vascular hydrostatic pressure
- left ventricular failure
- renal failure
- low capillary oncotic (colloid osmotic) pressure
- hypoalbuminaemia in hepatic cirrhosis, nephrotic syndrome
What are the causes of an exudate pleural effusion?
- inflammation with / without infection
- when does an acute inflammatory effusion become an empyema?
- neoplasms - primary or secondary
What are the symptoms and signs of pleural effusion?
What investigations would support the diagnosis?
symptoms:
- breathlessness - the effusion compresses the lung
- little / no pleuritic pain - the visceral and parietal pleura are not in contact
signs:
- dull to percussion
- reduced breath sounds on auscultation
investigations:
- imaging - ultrasound, CT, chest radiograph
How is breathlessness treated in a pleural effusion?
breathlessness is treated by removing the fluid
- aspiration with a needle and syringe (ultrasound guided)
- reaspirate if the fluid reaccumulates
- for recurrent effusions, consider a temporary or permanent pleural drain
- for recurrent effusions when the lung expands after drainage and the underlying cause remains, consider pleurodesis to obliterate the pleural cavity
What is the other important stage in treating pleural effusion?
identify and treat the underlying cause
local:
- pleural fluid for cytology, microbiology & biochemistry
- pleural biopsy
systemic:
- investigate the systemic causes of pleural effusion
What is pneumothorax?
What are the 2 different types?
air in the pleural cavity
it can be an open or closed pneumothorax
What is an open pneumothorax?
How does it work?
it is a chest wall perforation that is usually traumatic
a “sucking chest wound” connects the body surface to the pleural cavity
external air is drawn into the pleural cavity during inspiration, reducing lung potential expansion
What is a closed pneumothorax?
What is the result of this?
a lung perforation that is usually not traumatic connects the lung air spaces to the pleural cavity
lung air is drawn into the pleural cavity during inspiration, reducing potential lung expansion
What are the causes of closed pneumothorax?
ruptured emphysematous bullae
common inflammatory lung diseases:
- asthma, pneumonia, tuberculosis, cystic fibrosis
traumatic:
- lung tears from fractured ribs
iatrogenic:
- mechanical ventilation at high pressures
- lung and pleural biopsy procedures
rare:
- rare cystic lung diseases - Langerhans’ cell histiocytosis, lymphangioleoimyomatosis
- catamenial due to pleural endometriosis
What causes a tension pneumothorax?
the perforation into the pleural cavity in an open or closed pneumothorax can be valvular
this allows air into the cavity during inspiration but not out during expiration
the pressure in the pleural cavity can rise above atmospheric pressure
Why does tension pneumothorax require urgent treatment?
the rising pressure in the pleural cavity can compress mediastinal structures
e.g. vena cavae and heart
and it can move the mediastinum to compress the contralateral lung
this is potentially fatal
What are the symptoms and signs of pneumothorax?
symptoms:
- small ones may be asymptomatic
- breathlessness
- pleuritic chest pain
signs:
- cyanosis
- tachycardia
- contralateral tracheal deviation in tension pneumothorax
- percussion - hyperresonant
- auscultation - reduced breath sounds
What investigations support the diagnosis of pneumothorax?
- imaging - ultrasound, CT, chest radiograph
- symptomatic pneumothoraces are often initially treated without further investigation
What is the general treatment for pneumothorax?
What if they are recurrent?
the pneumothorax may resolve spontaneously
a chest drain tube can be inserted incorporating a valve to allow air out but not in whilst the pneumothorax resolves
pleurodesis is considered in recurrent pneumothoraces
What is different about treatment for tension pneumothorax and open pneumothorax?
tension pneumothorax:
- this can be decompressed as an emergency procedure using a needle inserted via an intercostal space
open pneumothorax:
- the penetrating chest wound causing it can be covered with an occlusive adhesive dressing that may incorporate a valve that allows air out but not in
What are the 2 different types of primary pleural neoplasms?
benign / low grade malignant:
- these are uncommon
- e.g. low grade mesothelial tumours
malignant:
- malignant mesothelioma is common
- others are uncommon
What is a secondary pleural neoplasm?
a secondary pleural neoplasm is malignant and has travelled from elsewhere
carcinomas:
- breast, lung are common
others:
- lymphoma
- melanoma
What is meant by malignant mesothelioma?
a neoplasm of the mesothelial cells that line serous cavities
this includes pleura, peritoneum, pericardium, tunica vaginalis
What % of malignant mesotheliomas are pleural?
Do they tend to affect more men or women?
92% are pleural and 8% are peritoneal
both are more common in men
they tend not to metastasise widely
What are peritoneal malignant mesotheliomas associated with?
peritoneal mesotheliomas affect a higher proportion of women
they have a higher proportion of low grade type
they are less strongly associated with asbestos dust exposure
Where does an early malignant mesothelioma tend to be located?
What can it produce?
Why is it difficult to diagnose?
a small tumour can produce a large pleural effusion
the tumour can be difficult to identify on imaging and therefore it is difficult to target biopsies at it
malignant cells may be shed into the effusion so effusion cytology may allow an early tissue diagnosis to be made
Where would an advanced malignant mesothelioma be located?
What is the histology of maligant mesothelioma like?
What is the main morphological differential diagnosis?
mixed tubulopapillary epithelioid & spindle cell sarcomatoid morphology
it can be either type alone
it can be poorly cellular - “desmoplastic”
the main morphological differential diagnosis is malignant mesothelioma or non-small cell carcinoma
What does the histology of malignant mesothelioma look like?
tubules and solid aggregates of malignant mesothelial cells
the morphological differential diagnosis is adenocarcinoma or epithelioid malignant mesothelioma
What is meant by immunostaining in malignant mesothelioma?
it uses antibodies linked to a dye to identify antigens in cells
mesothelial cells and epithelial cells tend to express different antigens, allowing them to be differentiated from each other
Why is a panel of antibodies used in malignant mesothelioma immunostaining?
What stains are shown in the images?
there is some cross reaction so a panel of 4 or more antibodies is used
top - cytokeratin 5
middle - Wilms tumour antigen
bottom - calretinin
What is the main cause of malignant mesothelioma?
asbestos accounts for 80-90% of cases
strong association with asbestos dust exposure above the general population exposure level (but exposure level can be quite low)
mesothelioma develops 15 years to over 60 years after exposure
risk increases with cumulative exposure level and time from exposure
What are other causes of malignant mesothelioma?
- thoracic irradiation
- BAP1 (BRCA1-associated protein 1) mutations
- germline mutations in a familial cancer syndrome with uveal melanomas and mesotheliomas
What is asbestos?
What is the diameter and the different types?
fibrous metal silicates 5-100um x diameter 0.25-0.5um
amphibole:
- blue asbestos (crocidolite)
- brown asbestos (amosite)
serpentine:
- white asbestos (chyrosotile)
What happens when asbestos is inhaled?
How can it be seen in tissue sections?
when inhaled, some become coated with mucopolysaccharides containing iron to form asbestos bodies
asbestos bodies can be seen in tissue sections by light microscopy
they are brown when unstained and blue when the iron is stained and quantified
How are asbestos bodies quantified?
asbestos fibres can be quantified in lung extracts by election microscopy
this is complex and expensive
Which types of asbestos are the most and least oncogenic?
amphiboles (particularly crocidolite) are the most oncogenic and persist in the lungs
chrysotile is less oncogenic and is more readily cleared from the lungs
What is erionite?
a fibrous zeolite mineral that has a fibre structure similar to asbestos
it is used as a building material in areas of Turkey where there is a high incidence of mesothelioma occurring in young people
What was asbestos used for?
a fire-proof material widely used in commercial and domestic buildings and in shipbuilding from 1940s to 1990s
there is still a lot present in buildings, presenting a risk to those working in or being near building maintenance and demolition process
What is high level of exposure to asbestos dust associated with?
it is an independent risk factor for lung carcinomas of all types
What are the pleural, lung and skin diseases associated with asbestos?
pleural:
- pleural effusion
- parietal pleural fibrous plaques
- diffuse pleural fibrosis
- malignant mesothelioma
lung:
- asbestosis
- lung carcinoma
skin:
- asbestos corns - benign hyperkeratotic wart-like skin lesions
