Although our case study showed the expression of neuroendocrine markers, such as CD56 and INSM1, with negativity for cytokeratin, NUT, desmin, and SS18-SSX, the retention of the Brg1 intranuclear stain can exclude the possibility of neuroendocrine carcinoma, NUT carcinoma, rhabdomyosarcoma, poorly differentiated synovial sarcoma, and the SMARCA4 deficient thoracic tumor, respectively. The gene discussed is INSM1; the disease is rhabdomyosarcoma.