Application of INSM1 in Diagnosis and Grading of Laryngeal Neuroendocrine Carcinoma

Objective Chromogranin (CHG), synaptophysin (Syn), and CD56 are generally used in a panel to support diagnoses of laryngeal neuroendocrine carcinomas (NECs). However, the absence of expression of these markers does not completely exclude the diagnosis. INSM1 is a novel marker that is considered sufficiently sensitive and specific for NE differentiation. The aim of this study is not only to detect its sensitivity and specificity, but also to evaluate its application in grading for laryngeal NECs. Methods The clinicopathological characteristics of the 25 cases with laryngeal NECs were retrospectively analyzed. The expressions of INSM1, CHG, Syn, and CD56 were detected by immunohistochemistry. Results Of the 25 laryngeal NECs, INSM1 had higher sensitivity (92%) than Syn (84%), CHG (76%) and CD56 (76%). The average H scores of INSM1, CD56, Syn, and CHG were 160, 37.5, 300, 300 for well-differentiated neuroendocrine carcinoma (WD-NEC); 190, 149, 209, 215 for moderately differentiated neuroendocrine carcinoma (MD-NEC); 251, 208, 104, 25 for poorly differentiated neuroendocrine carcinoma with small cell (SCNEC); 109, 160, 98, 26 for large cell types (LCNEC), respectively. Of these 98 non-neuroendocrine tumors, INSM1 expression was seen in nine (9%) tumors, all were squamous cell carcinoma. And INSM1 staining was generally focal. Conclusion INSM1 has high sensitivity and specificity in diagnosis of laryngeal NECs. For grading laryngeal NECs, Syn and CHG showed significant advantages in the diagnosis of WD-NEC and MD-NEC, whereas INSM1 and CD56 showed greater diagnostic value in the diagnosis of SCNEC and LCNEC, especially in SCNEC. Level of Evidence 4 Laryngoscope, 2021