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.