Recently, SMARCA4, an important part of the SWI/SNF chromatin remodeling complex, was found to play a major role in the development of some thoracic cancers. SMARCA4-deficient thoracic tumors are a special type of cancer because they don't produce SMARCA4 proteins. These tumors have been linked to aggressive behavior in patients and a unique histopathological profile. The goal of this review is to give a full picture of thoracic tumors that don't have SMARCA4, giving us clues about possible ways to target these tumors and make patient results better.