Non-Small-Cell Lung Carcinoma Subtyping on Cytology without the Use of Immunohistochemistry – Can We Meet the Challenge?

OBJECTIVE: Recent advances in lung carcinoma therapy have led to a new emphasis on the subtyping of non-small-cell carcinomas of the lung which has led pathologists to readdress the approach to small biopsies and cytology in lung cancer diagnosis. A minimum use of specimens for an accurate diagnosis and to preserve as much tissue as possible for potential molecular markers has been recommended. STUDY DESIGN: In this study we blind-reviewed 50 cases of cytologically diagnosed non-small-cell type lung carcinomas and categorized them into adenocarcinoma and squamous-cell carcinoma based on cytological features alone. Only those cases that had had a histological follow-up were selected. RESULTS: On blind review, a definitive categorization of non-small-cell carcinoma of the lung was made in 28 of 29 cases of adenocarcinomas and in 14 of 19 squamous-cell carcinomas. CONCLUSION: When attempted, most cases of well-to-moderately differentiated adenocarcinomas can be identified based on cytological features alone. Poorly differentiated squamous-cell carcinomas are more likely to be called non-small-cell carcinomas.