Abstract 5933: Improved identification of lung neuroendocrine neoplasms using INSM1 (SP493) Rabbit Monoclonal Primary Antibody

Abstract Introduction: About 20% of lung cancers are of neuroendocrine origin. In addition to evaluation of morphological features, these neoplasms can be identified by immunohistochemistry (IHC) using neuroendocrine markers such as synaptophysin, chromogranin A and neural cell adhesion molecule, CD56. Recent studies showed that INSM1 is increasingly used as a diagnostic marker for cancers of neuroendocrine origin, since it is highly sensitive and specific. The primary focus of this study was to assess the sensitivity and specificity of a newly developed assay that is using a new INSM1 (SP493) antibody in detecting neuroendocrine lung cancers and to compare this IHC assay with currently used neuroendocrine markers. Method: Tissue microarrays containing 292 lung tumors were stained with INSM1 (SP493) antibody, INSM1 (MRQ-70) antibody, CONFIRM anti-Synaptophysin (SP11) antibody, anti-Chromogranin A (LK2H10) antibody, and CD56 (MRQ-42) antibody on a BenchMark ULTRA instrument using OptiView DAB IHC Detection Kit or ultraView Universal DAB Detection Kit and sensitivity and specificity was calculated for each biomarker. Results: The sensitivity and specificity of this new assay with INSM1 (SP493) antibody were 92.5% and 95.8%, respectively. Similar results were obtained for the lung cancer cases stained with INSM1 (MRQ-70) antibody; the specificity was 90.6% and sensitivity was 95.9%. In contrast, anti-Synaptophysin (SP11) antibody and anti-Chromogranin A (LK2H10) antibody demonstrated considerably lower sensitivity when used to stain these lung cancer cases. The sensitivity was 79.7% and 75.8% for anti-Synaptophysin (SP11) antibody and anti-Chromogranin A (LK2H10) antibody, respectively. The specificity of anti-Chromogranin A (LK2H10) antibody was comparable with the specificity of the INSM1 (SP493) antibody (97.5%); while the specificity of anti-Synaptophysin (SP11) antibody was lower (90.8%). The performance of CD56 (MRQ-42) antibody was suboptimal with the sensitivity of 86.2% and the specificity of 84.9%. Conclusions: Overall, our data showed that the new IHC assay with INSM1 (SP493) antibody is highly specific and sensitive in detecting neuroendocrine lung tumors. Citation Format: Katerina Dvorak, Rafael Sainz, Alexander Gomez. Improved identification of lung neuroendocrine neoplasms using INSM1 (SP493) Rabbit Monoclonal Primary Antibody [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5933.