The Application and Diagnostic Utility of Immunocytochemistry on Direct Smears in the Diagnosis of Pulmonary

The importance of subclassifying pulmonary nonsmall cell carci-noma (NSCLC) in cytologic material is becoming increasingly paramount. Occasionally, cell blocks traditionally used for an-cillary studies are sparsely cellular or acellular. Hence, we investigated the diagnostic utility of immunocytochemistry for Napsin-A, TTF-1, and p63 on direct smears of NSCLC. Immuno-histochemistry for Napsin-A was initially tested on a tissue microarray (TMA) composed of pulmonary adenocarcinoma. Subsequently, in 25 cases, immunocytochemistry for Napsin-A, TTF-1, and p63 was performed on cytologic direct smears. Smears were prepared from tumor cells scraped from lung resection specimens (n 10), endobronchial ultrasound-guided transbronchial fine-needle aspirates (n 13), and pelleted cell material from pleural effusions (n 2). Immunohistochemistry uti-lizing the TMA revealed Napsin-A positivity in 73 % of pulmonar