Fine Needle Aspiration Cytology – Pulmonary

Rana S. Hoda MD, FIAC


Lower respiratory cytology is important in the evaluation of pulmonary disease. Diagnosis is achieved by evaluation of exfoliative cytology (sputum, bronchial brushing, bronchial wash, and bronchoalveolar lavage) and fine needle aspiration (FNA) cytology (percutaneous, transthoracic, transbronchial and endoscopic-ultrasound guided).

For optimal pulmonary cytology proper specimen collection, fixation and processing are imperative. Collection in Cytolyt® for preparing a ThinPrep® slide has shown to be an excellent technique for respiratory tract specimens and has overcome many limitations of conventional smears by reducing the number of slides to examine, eliminating air-drying artifact and limiting obscuring elements such as mucus, blood and inflammation. Residual material from the specimen vial can be used for ancillary studies, such as special stains for organisms.

The main diagnostic issues in pulmonary cytology include identification of organisms, distinguishing reactive type 2 pneumocytes from well differentiated bronchioloalveolar carcinoma, reactive bronchial epithelium from malignancy, adenocarcinoma from squamous cell carcinoma, non-small cell carcinoma from small cell anaplastic carcinoma and cytologic differential diagnosis of neuroendocrine tumors. On ThinPrep slides microorganisms are easier to find and the morphology is similar to conventional smears. Due to well-preserved nuclear features the differential diagnosis between reactive type 2 pneumocytes and bronchioloalveolar carcinoma is relatively straightforward.

The general features of pulmonary cytology prepared by ThinPrep technique, compared to conventional preparation methods include:


  • Decreased inflammatory cells
  • Decreased mucus
  • Background material appears clumped or in aggregates rather than diffuse

Architectural Pattern:

  • Uniform distribution of cells
  • Smaller cell clusters, fragments and sheets
  • Three-dimensional clusters can be seen
  • Slightly more dispersed cell pattern

Cellular Features:

  • Smaller cell size
  • Well-preserved cytoplasmic features
  • Well-preserved nuclei and nuclear detail
  • Prominence of nucleoli

Nuclear molding in small cell anaplastic carcinoma is subtle. It appears more like gentle nuclear overlap. Crush artifact can be seen either as spindled nuclei or as long blue fibrous structures.


  • Limited screening area
  • Additional slides can be prepared for ancillary tests
  • Reduction of obscuring elements
  • Less overlap, even distribution, almost monolayer distribution
  • Lack of air-drying


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  2. Wiatrowska BA, Krol J, Zakowski MF: Large-cell neuroendocrine carcinoma of the lung: Proposed criteria for cytologic diagnosis. Diagn Cytopathol 2001; 24:58-64.
  3. Zimmerman RL, Montone KT, Fogt F, Norris AH: Ultra fast identification of Aspergillus species in pulmonary cytology specimens by in situ hybridization. Int J Mol Med 2000 Apr; 5(4): 427-9.

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