AbstractIntroductionPulmonary nuclear protein of the testis (NUT) midline carcinoma (NMC) is a aggressive cancer with t (15, 19) translocation. Here we present the clinicopathological characteristics and molecular genetics alterations of primary pulmonary NMC.MethodsFluorescence in situ hybridization (FISH) assay was performed to evaluate NUT translocation. Next generation sequencing (NGS) was performed to investigate genomic landscape. A panel of 289 lung cancer tissues with undifferentiation was retrospectively screened for NUT expression by immunohistochemical (IHC) assay.ResultsOverall, 2136 lung cancer samples were reviewed. We consecutively identified 12 cases of primary pulmonary NMC. Computed tomography revealed centrally located bulky lung mass with ipsilateral mediastinal lymph node and pleural involvements. Tumor cells presented diffuse poor differentiation and focal squamous differentiation with positive NUT expression. NUT rearrangement was confirmed by FISH assay. Ten NMC samples were investigated by NGS. The most common alterations identified were P53, PIK3CA, AUTS2, ITIH2, and CDKL5 genes. Pulmonary NMC exhibited increased activity of PI3K/AKT pathway. In the screening study, BRD4‐NUT rearrangement was identified in two cases.ConclusionNUT rearrangement remains the gold standard in the diagnosis of pulmonary NMC. PI3K inhibition is a potential targeted therapy for pulmonary NMC.