CONTENT:

6.3 Lung Cytology
6.3.1 Lung Samples for Cytology
i. Sputum
ii. Bronchial Brushings and Washings
iii. Broncho-alveolar Lavage (BAL)
iv. Fine Needle Aspiration (FNA) Cytology
6.3.2 Sensitivity of Lung Cytology
6.3.3 Diagnostic Categories for Reporting Lung Cytology
6.4 Histological Examination of Lung Tissue

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6.3 Lung Cytology

 
Cytology samples are usually obtained during bronchoscopy and are called ‘bronchial brushings’ and ‘bronchial washings.’  Cytology samples may also be obtained during endobronchial ultrasound (EUS) examination. These samples fixed in alcohol or acetone, spun down, smeared onto a glass slide and stained with histochemical dyes (PAP, H&E or modified Giemsa) to allow the cells to be analyzed using light microscopy.

Figure 6.3 Lung Cytology.

A. Photomicrograph of lavage fluid shows irregular, large cells,
some with foamy and vacuolated cytoplasm. This is a non small
cell carcinoma, with features of adenocarcinoma. B. Photomicrograph
of a sputum cytology sample shows malignant cells (blue) with keratin
formation (orange) consistent with squamous cell carcinoma.
C. Photomicrograph of the cytology of bronchial brushings shows
cohesive, small malignant cells with little cytoplasm, consistent with
small cell carcinoma. (PAP x 60)

6.3.1 Lung Samples for Cytology

i. Sputum

 
Sputum for cytology is obtained as ‘spontaneous’ or ‘induced’ samples. Sensitivity for diagnosis of lung cancer increases with the ‘adequacy‘ of the samples; usually between 3 to 5 samples are needed. A minimum of 2 smears per sample is prepared, and a cell block preparation can be made if there is sufficient material.
 

ii. Bronchial Brushings and Washings

 
Sensitivity of the bronchoscopic samples for diagnosing bronchogenic lung cancer is dependent on the experience and skill of the endoscopist; it can be similar to the sensitivity of a bronchial biopsy.

Bronchial washings and brushings can either be prepared on-site and fixed with alcohol or the brush can be rinsed in cytology fixative.
 

iii. Bronchiolo-alveolar Lavage (BAL)

 
Bronchiolo-alveolar lavage (BAL) is used to assess the contents of the terminal airspaces.
 

iv. Fine Needle Aspiration (FNA) Cytology

 
Fine needle aspiration (FNA) cytology is performed for the evaluation of localized pulmonary lesions and mediastinal sampling in the context of lung cancer.

The techniques used include transthoracic percutaneous FNA, transtracheal/transbronchial FNA, endobronchial ultrasound-assisted needle aspiration (EBUS-FNA) or endoscopic ultrasound-assisted FNA (EUS-FNA) (performed via the esophagus).

The cytology specimens may be triaged for microbiology, flow cytometry, cell blocks or smears.

Air-dried slides with ‘Diff-Quik’ cell staining are used for rapid on-site evaluation. Some slides may also be fixed with an alcohol solution and stained with H&E or Papanicolaou (PAP) stain.

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6.3.2 Sensitivity of Lung Cytology

 
Published studies by the College of American Pathologists (CAP) have shown that the sensitivity of FNA lung cytology for the diagnosis of lung cancer ranges from 50 % to more than 90 %.  The specificity is close to 100%. The ‘false positive’ rate is less than 1%, and the ‘false negative’ rate (usually due to poor sampling) is approximately 10%.

Sensitivity

Sputum:

Central tumors                        71%

Peripheral tumors                   49%

Bronchial Brushings:

Endobronchial tumors             59%

Peripheral tumors                     52%

Bronchial Washing/Lavage:

Endobronchial tumors             48%

Peripheral tumors                     43%

Transthoracic FNA                    90%

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Specificity measures the percentage of healthy people correctly identified as not having the disease.

6.3.3 Diagnostic Categories for Reporting Lung Cytology

 
Cytology samples can be preserved and prepared for light microscopy quite quickly. For reporting of the cytology findings, the following diagnostic criteria may be used:
 

i. Unsatisfactory/Non-Diagnostic

 
A diagnosis cannot be made because the specimen is of very low cellularity, is obscured by blood or the cells are poorly preserved.
 

ii. Benign/Non-Malignant

 
A cytology sample must be satisfactory (adequate) for evaluation for a benign diagnosis to be made.
 

iii. Atypical

 
This classification is for cells that are not clearly benign or malignant and show cells that carry likelihood of malignancy. Definitive diagnosis may not be possible in such cases due to lack of clear cellular morphological features, few cells, obscuring blood and poor cell preservation.
 

iv. Suspicious for Malignancy

 
The cellular appearances strongly favor cancer, but the morphological appearances or the low cellularity prevent a definitive diagnosis.
 

iv. Malignant

 
Because of its high specificity, a malignant cytological diagnosis is interpreted as a definitive diagnosis and is only be made when there are definitive morphological features in a satisfactory and optimal specimen. The diagnosis of malignancy should be further qualified, if possible.

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6.4 Histological Examination of Lung Tissue

 
Lung tissue removed as part of a biopsy procedure is sent to the Pathology Laboratory. The lung tissue is received and described by the Pathologist, who selects small pieces for further examination.

The small lung tissue samples are further processed in fixatives or preservatives that include formalin; they are embedded in paraffin wax, sliced very thinly and mounted on glass slides. The thin tissue sections are stained with ‘histochemical’ cell dyes, to allow for assessment of cells and tissues under the microscope.  The process of tissue fixation, processing, sectioning and histochemical staining takes at least 24 hours to complete.

The fixed and processed lung tissue samples may be stored for years to be available for sectioning and examination again, as formalin-fixed, paraffin-embedded (FFPE) samples.

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REFERENCES:

Böcking A, Klose KC, Kyll HJ, Hauptmann S. (1995). Cytologic versus histologic evaluation of needle biopsy of the lung, hilum and mediastinum. Sensitivity, specificity and typing accuracy. Acta Cytol. 39(3), 463. (Retrieved 19^th Feb 2015). http://www.ncbi.nlm.nih.gov/pubmed?term=7762333

Hammar SP. (2006). Macroscopic, histologic, histochemical, immunohistochemical, and ultrastructural features of mesothelioma. Ultrastruct Pathol. 30(1), 3. (Retrieved 10^th Feb 2015): http://informahealthcare.com/doi/abs/10.1080/01913120500313143

More references for this section are on this page .

PATIENT INFORMATION:

Cancer.Net Lung Cancer: Diagnosis (Retrieved 26^th April 2015): http://www.cancer.net/cancer-types/lung-cancer/diagnosis

Patient UK Lung Cancer (Retrieved 26^th April 2015): http://www.patient.co.uk/doctor/lung-cancer-pro

More patient information for this section is on this page .

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