Thoracic tumors with SMARCA4 deficiency comprise two subtypes: SMARCA4-deficient undifferentiated tumors and NSCLC with SMARCA4 deficiency.9) Considering the fact that SWI/SNF complex deficiency is found in gastrointestinal malignancies, similar observations may be suggested in other types of cancers. Here, SMARCA4 is linked to neoplasm of thorax.