Cytologic evaluation of the respiratory tract.

Evaluation of respiratory tract disease is a challenge for several reasons: no serum biochemical or hematologic tests that localize injury to the respiratory system are available, imaging techniques do not usually lead to etiologic diagnoses, and excisional biopsies are often very difficult to obtain from respiratory lesions. For these reasons, specific diagnosis of respiratory tract disease often resides in cytologic evaluation. This article reviews the various cytologic collection techniques that yield high-quality specimens from the upper and lower respiratory tract. Cytologic features of the normal respiratory tract as well as common respiratory disorders are described and illustrated.