A thoracic SMARCA4-deficient undifferentiated tumor: A case report.

Thoracic SWI/SNF-related BAF chromatin remodeling complex subunit ATPase 4 (SMARCA4)-deficient undifferentiated tumor (SMARCA4-UT) is a newly recognized, high-grade malignant neoplasm that is rare in clinical practice. There is no standardized or clearly defined treatment protocol for SMARCA4-UT in clinical guidelines. The current study reports the case of a 54-year-old male patient who presented with a 2-month history of an intermittent productive cough. Bronchoscopy demonstrated a neoplasm in the anterior segment of the right upper lobe bronchus, which almost obstructed the lumen, with a hypervascular surface, suggestive of a right upper lobe carcinoma. Histopathological examination confirmed a poorly differentiated carcinoma. Immunohistochemical analysis demonstrated a SMARCA4 gene mutation in exon 4, classifying the tumor as SMARCA4-deficient undifferentiated lung carcinoma. The patient developed superior vena cava syndrome (SVCS), requiring emergent percutaneous stent placement. Treatment also included computed tomography-guided cryoablation and radiofrequency ablation (RFA), alongside targeted molecular therapy with crizotinib. Despite aggressive multimodal therapy, the patient succumbed to tumor thrombosis at 1 month post-treatment. Overall, SMARCA4-UT is rare and diagnostically challenging, lacking standardized treatment guidelines. In clinical practice, cryoablation with argon-helium and RFA may provide palliative benefits by alleviating tumor burden and improving quality of life. Endovascular intervention provides a rapid and effective approach to alleviate tumor-induced SVCS. However, subsequent anticoagulation and antineoplastic therapies require further investigation to determine their efficacy in the management of such cases.