The diagnostic value of TTF-1, CK 5/6, and p63 immunostaining in classification of lung carcinomas. 
This study was aimed to evaluate the utility of a panel of antibodies, consisting of thyroid transcription factor-1 (TTF-1), p63, and cytokeratins (CK) 5/6 for distinguishing between small cell lung carcinoma (SCLC) and nonsmall cell lung carcinoma, as well as for identifying glandular or squamous differentiation in small tissues obtained by bronchoscopy.  Bronchoscopic biopsies of 77 lung carcinoma cases with easily recognizable morphologic features were included in this study.  All the cases were immunohistochemically stained for p63, CK5/6 [indicators of squamous cell carcinoma (SCC)] and TTF-1 [indicator of SCLC and adenocarcinoma (AC)].  Although, 28 SCLC displayed TTF-1 positive, p63 negative immunoprofile, most of the SCC (32/39) had the opposite immunoprofile.  All of the 10 ACs were negative for p63 and most of them (8/10) were negative for CK5/6.  p63 and CK 5/6 seem to be useful for differentiating AC and SCLC from SCC with 100% specificity and 82% sensitivity, 89% specificity and 79% sensitivity, respectively.  It seems that to achieve histologic typing of lung cancer as accurate as possible, TTF-1 in combination with p63 and CK 5/6 might be useful components of immunohistochemical analysis of poorly differentiated lung carcinomas in biopsy tissues.