Abstract: Objective To investigate the value of detecting thyroid transcription factor 1 (TTF-1) and Noval aspartic proteinase of
pepsin family A (napsin A) in pleural fluid cell blocks in cytopathologic diagnosis of pulmonary adenocarcinoma. Methods
Conventional cell smears of pleural effusions were obtained from 48 patients with a history of lung adenocarcinoma for
cytological analysis. The cell blocks were prepared using the cytological specimens and examined with immunohistochemistry
for TTF-1 and napsin A. The rates of a positive diagnosis of pulmonary adenocarcinoma were compared between the two
methods, and the diagnositic value of TTF-1 and napsin A in pleural fluid cell blocks was evaluated. Results Immunohistochemistry
of the cell block sections yielded a significantly higher positive rate of diagnosis than cytological analysis of
conventional cell smear (84.44% vs 55.56%, P<0.05). Most of the pleural fluid cell blocks showed positive expressions of TTF-1
(36/38, 94.74%) and napsin A (30/38, 78.95%), and none of samples showed TTF-1 or napsin A expression in the mesothelial
cells (P<0.05). The combination detection of TTF-1 and napsin A in pleural fluid cell blocks had a high diagnosis value with a
diagnostic sensitivity of 97.37% and a specificity of 100% for pulmonary adenocarcinoma. Conclusions The combined
detection of TTF-1 and napsin Ain pleural fluid cell blocks facilitates cytopathologic diagnosis of pulmonary adenocarcinoma.