Respiratory cytology: a review of non-neoplastic mimics of malignancy.

Respiratory cytology has its share of pitfalls. Some, such as vegetable cell contaminants, pose problems for only inexperienced observers, while others, such as reactive bronchoalveolar cells from pneumonia, can lead even experienced cytopathologists to make a misdiagnosis of malignancy. This review illustrates and analyzes those benign conditions or entities known to mimic malignancy in exfoliative respiratory cytology and fine-needle aspiration biopsy of the lung. Entities are grouped by the type of malignancy they mimic, and guidelines are presented for avoiding specific pitfalls.