@article {Zahelp1965, author = {Tina Zahel and Arne Warth and Esther Herpel and Benjamin Goeppert and Albrecht Stenzinger and Sabine Krysa and Hans Hoffmann and Peter Schirmacher and Philipp Schnabel}, title = {Contribution of immunohistochemical (IHC) markers to the diagnosis of pulmonary carcinoids}, volume = {38}, number = {Suppl 55}, elocation-id = {p1965}, year = {2011}, publisher = {European Respiratory Society}, abstract = {Introduction: Data about prevalence and clinicopathological meaning of IHC markers in pulmonary typical (TC; n=114) and atypical (AC; n=86) carcinoids is still debated. The goal of this study was to present expression patterns of several IHC markers in TC and AC, to get an insight on differential diagnostic, prognostic, and potential therapeutic value.Methods: 200 pulmonary carcinoid tumors were investigated for tissue distribution of: CD56, CD57, Chromogranin A, Synaptophysin, TTF-1, CK18, KL1, ERCC1, EGFR, and Her-2/neu. Ki67 was employed and the proliferative index (PI) was counted on whole slides of resected specimens.Results: Mean PI was 1.8\% in TC and 3.7\% in AC and was significantly different in both groups (p\<0.0001).Correlation between PI and mean mitotic count was significant. Furthermore, max PI correlated significantly with outcome. Established neuroendocrine markers Synapthophysin, Chromogranin A, and N-CAM (CD56) were strongly positive. Synaptophysin was expressed with highest intensity of all markers in 95.4\% TC and 98.6\% AC. Thyroid transcription factor 1 (TTF-1) was positive in 73.0\% TC and 77.0\% AC. Only few cases expressed EGFR and Her2/neu.Conclusions: Synaptophysin may be the most sensitive marker for neuroendocrine differentiation. Nevertheless, there is no specific marker to clearly separate TC from AC. We confirm that the PI, as determined by Ki67 staining is higher in AC than in TC and might be an ancillary tool for the distinction between TC and AC in addition to the mitotic rate. Moreover, the combination of PI and mitotic count in terms of a grading system may predict outcome more effectively than mitotic count alone and should be subject to further research.}, issn = {0903-1936}, URL = {https://erj.ersjournals.com/content/38/Suppl_55/p1965}, eprint = {https://erj.ersjournals.com/content}, journal = {European Respiratory Journal} }