The mutational inactivation leading to SMARCA4 deficiency, partly similar histomorphological features and the loss of anti-BRG1 IHC expression with predominantly having transcriptomic similarities to BAF-deficient sarcomas, these SMARCA4-deficient thoracic tumors were initially under the umbrella of SMARCA4-deficient thoracic sarcomas (DTS) [14]. The gene discussed is SMARCA4; the disease is neoplasm of thorax.