Module 10 Part 1 - Respiratory Tract Cytopathology Flashcards
Histology of Respiratory Tract
Squamous epithelium - non keratinising stratified
Respiratory epithelium- pseudostratified columnar
- ciliated
- mucus secreting goblet cells
- non-ciliated and cuboidal cells in smaller bronchi
- Clara cells: produce surfactant
Kulchitsky cells: are specialised neuroendocrine cells
Alveoli
- lined by two types of epithelium
- type I pneumocytes: thin walled and have a large surface area, a combination that facilitates gas exchange
- type II pneumocytes: more cuboidal and secrete surfactant
Pulmonary alveolar macrophages large phagocytic cells containing dust particles
Sputum Sample - Advantages and Disadvantages
Advantages - easily obtained - extensive area smapled - good for central tumors - accurate diagnosis - best screening test Disadvantages - difficult to obtain if not spontaneous - poor for peripheral lesions - benign tumors difficult to diagnose - less accurate for AdenoCa, metastasis and lymphomas
Criteria for Assessing Adequacy of Sputum Samples
Presence of pulmonary macrophages
Preservation or air-drying of specific samples
Fixation usually 95% ethanol or acetic acid
Bronchial Washing
Obtained using a flexible fibre-optic bronchoscope
Samples are mucoid in consistency and material is suspended in saline
Preparation from these samples require centrifugation at 1500rpm for 10 mins to sediment deposit
Indications for bronchoscopy include:
- cough, haemoptysis, bronchial obstruction, atelectasis (partial lung collapse)
Bronchial Brushing
Material is directly brushed or scraped from a lesion during a bronchoscopy
Brushing have a higher diagnostic yield for metastatic carcinoma, peripheral tumours and large necrotic cancers
Bronchiolar-Alveolar Lavage (BAL)
Performed for the assessment and monitoring of interstitial lung disease
Useful tool for obtaining material for cytology and microbiology from immunocompromised individuals with diffuse pulmonary infiltrates
Performed when saline is instilled and aspirated in serial washes through a fibre-optic bronchoscope
Fine Needle Aspirations (FNA)
Material is directly removed from a lesion using a syringe
Percutaneous (most common) and transbronchial
Skin, chest wall and pleural anaesthetized.
Under CT/US guided imaging
Slides are stained by H&E stain and examined immediately to determine specimen adequacy
Possible Complications for FNA
Pneumothorax (collapsed lung)
Haemorrhage
Air embolism
Needle track seeding
Benign Epithelium - Bronchial Epithelial Cells
Less common in sputum samples
Readily seen in post bronchoscopy samples
Shed in sheets and cohesive aggregates
Tall columnar appearance with a basophilic homogenous cytoplasm
Terminal plate may be visible on the apical surface with or without cilia
Benign Epithelium - Bronchiolar Epithelium
Lined by 2 kinds of pneumocytes, type I and type II
Type I alveolar pneumocytes are flat cells which cover > 90% of the alveolar surface
- not usually identified on cytology samples
Type II alveolar pneumocytes are columnar cells that are normally found scattered in the alveoli and secrete surfactant
- usually recognised when they become hyperplastic (reactive)
Pulmonary Macrophages
Cytoplasm finely vacuolated and usually contains phagocytosed dust particles
Oval or bean shaped, eccentric nucleus
Chromatin finely and evenly distributed, occasionally prominent nucleoli is visible
Characterised by their cytokine profile
They fight against pathogens by activating multiple immunological pathways and serve as a first line of defence
Have anti-inflammatory response to protect excessive tissue damage
Non-Cellular Elements
Curschmann Spirals
- casts of small bronchioles formed by impacted mucin, found in excess mucus production
- e.g. asthma
Ferruginous bodies
- form when iron salts precipitate into tiny rounded or fibrous inhaled dust
- the fibre is often asbestos but can be fibreglass
Alveolar proteinosis
- due to an enzymatic disorder of macrophages results in coarsely granular, PAS + debris
Corpora amylacea
- concentrically laminated calcified bodies, associated with BAC but also seen in TB
Non-Specific Reactive Changes
Reactive squamous cells Anucleate keratinized squamous cells Hyperplasia of bronchial epithelium Reactive bronchiolar cells Squamous metaplasia
Asthma
During an acute attack there is extensive loss of bronchial epithelium associated with extensive mucous and serous fluid into the bronchial lumen
Eosinophils are present in this exudate which forms mucoid plugs in the airways
Cytological findings include:
- visible mucus plugs seen in lavage fluid
- bronchial cells may appear in clusters ‘Creola bodies’
- eosinophils and Charcot Leyden Crystals
- Curschmann spirals
- inflammatory debris may contain fungal hyphae
Fungal Infections - Aspergillus
Pulmonary aspergillosis is caused by Aspergillus fumigatus and has a number of clinical syndromes, including:
- invasive pulmonary aspergillosis (IPA),
- chronic pulmonary aspergillosis (CPA)
- allergic bronchopulmonary aspergillosis (ABPA)
- Aspergilloma
Aspergillosis - Cytological Features
Hyphae
Dichotomous branching - 45 degree angles
Fruiting heads form in aerobic conditions
Stained by Papanicolaou and Grocott methods
Branches are refractile under polarized light microscopy
Fungal Infections - Cryptococcosis
Two main forms:
1. Cryptococcosis Gattii- restricted geographical distribution
2. Cryptococcosis Neoformans - causes human disease especially in immunocompromised individuals
Cryptococcus Neoformans is an environmental fungus and an emerging opportunistic pathogen, causing focal and disseminated infection
- commonly found in soil and in pigeon poop (lol poop!)
- eucalyptus trees and decaying wood
Often infection lungs and meninges
Cryptococcosis - Cytological Features
Cryptococcus is an encapsulated yeast which may show budding but no true hyphae
A single bud may be visualised attached via a narrow isthmus.
Non-encapsulated forms can occur in AIDS patients
The thick mucoid capsule stains pale and translucent with Pap and MGG stains
- stains magenta with PAS and Mucicarmine stains
Herpes Simplex Virus (HSV)
HSV of the respiratory tract can occur anywhere from the oral cavity to the alveoli
Immunocompromised patients, prolonged intubation, burns, neonates and neoplasia are all at risk of infection
Dx can be made on cytological material, sputum, BrBr, BrWsh, BAL and further clarification of diagnosis includes IHC, molecular techniques (ISH) and cultures
HSV - Cytological Features
Multinucleation Nuclear moulding ‘Ground glass’ appearance Loss of chromatin pattern Nuclear inclusions Clean background Exclude contaminant from URT
Pneumocystis Jirovecii
An opportunistic organism which results in life threatening pneumonia in patients who are immunocompromised
Infection occurs but the individual is asymptomatic, because of the organism’s low virulence
Common symptoms if not asymptomatic:
- fever
- dry cough
- SOB
- dyspnea on exertion
Pneumocystis Jirovecii - Cytological Features
CXR – bilateral infiltrates
Amphophilic proteinaceous alveolar casts
Honeycomb appearance of unstained cysts on Pap stain
Trophozoites outside cyst are not visible
If PJP is untreated, it often leads to death
Special Stains for Pneumocystis
MGG Methanamine Silver Cresyl Violet Toluidine Blue Acridine orange stain Immunocytochemistry EM
Laboratory and Dx Tests for PJP
Blood chemistry
Arterial blood gases
Serologies, antigen testing and molecular typing
Sputum (least invasive)
BrWash, BAL and transbronchial biopsy - dx yield 82-94%
Open lung biopsy - increased risk of morbidity
Features of an Unsatisfactory BAL Sample
Contain < 2x10^6 total cells
Fewer than 10 alveolar macrophages
Contain excessive numbers of epithelial cells
Contain mucopurulent exudate of PMN’s
Heavily bloodstained due to traumatic procedure
Contain degenerative changes due to artefacts, poor preservation etc.
