Wang M, Abi-Raad R, Baldassarri R, et al. - This study was carried out to assess potential nonspecific Insulinoma-associated protein 1 (INSM1) expression in non–small cell non-neuroendocrine lung cancers (NSCNELCs), particularly in squamous cell carcinomas (SqCCs) with basaloid features to avoid diagnostic pitfalls. Researchers constructed tissue microarrays for 324 NSCNELCs, including 196 adenocarcinomas, 86 SqCCs, and 42 other NSCNELCs. The results indicate that INSM1 is expressed in a significant subset of NSCNELCs, suggesting caution in interpreting INSM1 staining, particularly with limited samples. INSM1 should not be applied as a stand-alone neuroendocrine marker in differentiating primary lung tumors.