INSM1 was positive in 305 of 402 tumors with expected neuroendocrine differentiation (typical and atypical carcinoids, large cell neuroendocrine carcinomas, small cell lung cancers, and paraganglioma; sensitivity: 76%).
INSM1 was positive in 48 of 52 primary lung neuroendocrine neoplasms (92%), including 38 of 41 SCLCs (93%), the only LCNEC (100%), and 9 of 10 carcinoid tumors (90%), and it was negative in all 22 non-neuroendocrine primary lung tumors.
INSM1 also stained all (100%) of the atypical carcinoids, typical carcinoids and mediastinal paragangliomas, but only 3.3% of adenocarcinomas and 4.2% of squamous cell carcinomas.