Cytomorphological features of lymphoepithelial carcinoma of the lung - a comparative analysis of aspiration and exfoliative cytology

Background Lymphoepithelial carcinoma of the lung shows distinctive histologic features but its cytologic description is limited in the literature. This study reviews and compares a large cohort of lung and lymph node aspirates, bronchial, serous fluid, and sputum exfoliative cytology from histology-proven cases, aiming to detail diagnostic features and cytologic specimen types preferable for diagnosis of this entity. Methods Cytology specimens of patients with a histologic diagnosis of lymphoepithelial carcinoma on lung biopsy or resection were reviewed for cytomorphologic features associated with lymphoepithelial carcinoma, with comparison between cytologic specimen types performed. Results Totally 13 aspiration (7 lung and 6 lymph node) and 22 exfoliative (18 bronchial, 1 serous fluid and 4 sputum cytology) specimens were reviewed. The most common cytomorphologic features observed were macronucleoli (82.9%), marked nuclear membrane irregularity (82.9%) and naked tumor nuclei (74.3%). High cellular cohesion, presence of large tumor fragments, rich lymphoid background, and tumor-infiltrating lymphocytes, are also frequently seen (>60%). Lymphoid components, multinucleated tumor cells and large epithelial fragments were more commonly seen in aspirations compared to exfoliative specimens (p<0.05). Conclusion Distinctive morphological features of lymphoepithelial carcinoma of lung are reproducible on cytologic specimens. Qualitative nuclear features (macronucleoli, marked nuclear membrane irregularity and naked tumor nuclei) are the most consistently observed. Compared to exfoliative cytology, aspirated specimens show higher yield for diagnostic cytomorphologic features of lymphoepithelial carcinoma.