Contribution of immunohistochemistry in the differential diagnosis of non-small cell lung carcinomas on small biopsy samples.

PURPOSE Targeted therapy increases survival and the quality of life of non-small cell lung cancer (NSCLC) patients but it needs precise histological subtyping. The present study evaluated 6 monoclonal antibodies for the differential diagnosis of NSCLC on small-sized tissue samples. METHODS 50 small-sized tissue samples were obtained by bronchoscopy or fine needle aspiration biopsy (FNAB). According to morphology before immunohistochemistry 2 squamous cell carcinomas (SCC), 6 adenocarcinomas (AC), 9 NSCLC-probably SCC, 11 NSCLC-probably AC and 22 unclassified NSCLCs were diagnosed. Thyroid transcription factor-1 (TTF-1), cytokeratin 5/6, cytokeratin 7, p63, and the neuroendocrine markers CD56 and synaptophysin were used in the differential diagnosis of NSCLC. RESULTS After immunohistochemistry 13 (26.0%) SCC, 27 (54.0%) AC, 3 (6.0%) NSCLC with neuroendocrine differentiation (NSCLC-NE) and 7 (14.0%) NSCLC- unclassified were diagnosed. Twenty-two NSCLC- unclassified were further diagnosed as SCC (n=7), AC (n=7) NSCLC-NE (n=2) and 6 remained NSCLC- unclassified. Significant difference was found between definitely diagnosed 8 NSCLCs and 15 ACs (20.5 vs. 38.57percnt;, p=0.008). TTF-1 and cytokeratin 7 were expressed in 85.2% (23/27) of AC, and cytokeratin 5/6 and p63 in 100% (13/13) of SCC. Positivity of CD56 and synaptophysin in 3 NSCLC determined NSCLC-NE. CONCLUSION No one monoclonal antibody is totally specified for one histological type of tumor and its origin. Combination of TTF-1, cytokeratin 7, p63, cytokeratin 5/6, CD56 and synaptophysin allows for differentiation of NSCLC but Napsin-A for AC differentiation and chromogranin A for NSCLC-NE differentiation should be added in an optimal panel.