SMARCA4 and non-small cell lung carcinoma: However, recently, the fifth edition of the World Health Organization (WHO) classification recognized the thoracic SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) as a separate entity from conventional NSCLC with SMARCA4 deficiency because of its distinct histology, immunohistochemical profile, clinical features, and prognosis, placing it under the category of “other epithelial tumors of the lung” [2].