Lower respiratory tract cytology

Specimen:

Sputum sampling: is non-invasive, cheap and easily repeated.

For reliable diagnosis of malignancy three separate specimens, one per day should be collected into a sterile dry specimen container. 

Sputum does not deteriorate overnight if refrigerated; however longer delays may require pre-fixation of the sample in an equal volume of 70% alcohol. 

Early morning specimens are the most suitable.

Bronchial washings: can be obtained by instilling normal saline into the bronchus and withdrawing the fluid by suction. 

Material is submitted intact in a dry sterile container.

Bronchial brushings: using a flexible bronchoscope a brush sample may be obtained from the surface of the tumour under direct vision. 

Material from the brush is then wiped onto microscope slides which may be fixed in alcohol or air-dried depending on the laboratory protocol. 

This procedure is frequently combined with bronchial washings.

Transbronchial fine needle aspiration: wet fixed and air dried smears (see FNA section) and rinse needle in non-fixative solution.

Bronchoalveolar lavage: sampling of peripheral airways and alveolar spaces is accompanied by wedging the tip of a bronchoscope in a subsegmental bronchus and instilling and aspirating aliquots of normal saline into a trap. 

All the aspirated material is submitted into a sterile dry container.

Method:

Papanicolaou, Wrights or Romanowsky staining of submitted material after preparation. 

Ancillary techniques including cell block preparations and immunohistochemistry may be performed.

Application:

Investigation of inflammatory and infective diseases of the respiratory tract, non-infective granulomatous lung disease, interstitial lung disease, investigation of bronchopulmonary and metastatic tumours.

Interpretation:

Findings include features of malignant disease, asbestos bodies, fungal, viral and protozoal infection (eg, CMV, Aspergillus, Cryptococcus, Pneumocystis) and eosinophils (allergic bronchopulmonary disease).

Reference:

Gray W and Kocjan G eds. Diagnostic Cytopathology.  3rd ed. Churchill Livingstone 2010.

Kini SR. Colour Atlas of Pulmonary Cytopathology. Springer-Verlag 2002.