[Clinical characteristics and prognosis analysis of 17 cases of SMARCA4-deficient chest tumors].

Objective: To analyze the clinical characteristics and prognosis of 17 patients with pathologically confirmed SMARCA4-deficient chest tumors. Methods: Seventeen patients with SMARCA4-deficient thoracic tumors diagnosed by pathology in the Affiliated Hospital of Jining Medical University from September 2021 to January 2023 were collected through Results Query System of Pathology Department, and the patients' general conditions, clinical symptoms, tumor markers, imaging features, treatment and regression were retrospectively analyzed, and literature review was performed. Results: A total of 17 patients were included in this study. Their clinical characteristics were characterized as follows: male/female=16/1, age 42-74 years, mean (64.0±5.7)years. Only 1 female had no clear smoking history, and 16 males had a smoking history, of whom 1 had 5 smoking pack-years, and the remaining 15 case had a smoking history of 20-100 smoking pack-years, with a mean of (68.5±44.5) smoking pack-years. Clinical symptoms were mainly cough and sputum, followed by chest tightness, hemoptysis and chest pain. Tumor markers CYFRA19-9 was elevated in 9 cases (3.79-16.61 ng/ml), CEA was elevated in 8 cases (5.37-295.93 ng/ml), and NSE was elevated in 6 cases (17.18-70.37 ng/ml). Imaging manifestations were intrapulmonary or mediastinal mass shadows, and the tumor involved the mediastinum in 9 cases, the upper lobe of the right lung in 6 cases, the upper lobe of the left lung in 5 cases, the lower lobe of the right lung in 3 cases, the lower lobe of the left lung in 3 cases; cervical or supraclavicular lymph node metastasis in 8 cases, pleural metastasis in 4 cases, hepatic metastasis in 3 cases, cerebral metastasis in 3 cases, bone metastasis in 2 cases, and subcutaneous metastasis in 1 case. Combining immuno-histochemistry and pathology, there were 6 cases of SMARCA4-deficient NSCLC and 11 cases of SMARCA4-deficient undifferentiated tumor. Eight patients were treated with platinum-contained chemotherapy agents, four of which were combined with immune checkpoint inhibitors, and one was treated with enzatinib; only one of the 9 patients achieved partial remission after treatment, and the remaining eight had progression of the tumors on chest CT after treatment. Five patients abandoned the treatment, and died in 6-month of follow-up. Three patients underwent surgery for resection, and there was no significant progression in the three patients in the 6 months of follow-up. Conclusions: Clinically, middle-aged and elderly men with a history of heavy smoking should be given high priority, especially in patients whose imaging mostly showed intrapulmonary, especially in upper lobes, and/or mediastinal masses, rapid lesion progression, and early distant metastasis, and who should be alerted to the possibility of SMARCA4-deficient thoracic tumors. Late clinical stage is a high risk factor for poor overall patient survival, and platinum-containing chemotherapy agents combined with immune checkpoint inhibitor therapy may be effective, and early surgery may improve patient prognosis.

A Single-center Experience of Radiotherapy in Pediatric Ewing Sarcoma/Primitive Neuroectodermal Tumor of the Chest Wall.

AIM: To evaluate the treatment results, prognostic parameters, and treatment-related toxicity in patients with Ewing sarcoma (ES)/primitive neuroectodermal tumor (PNET) of the chest wall who underwent surgery, chemotherapy, and radiotherapy (RT) in a tertiary referral center. METHODS: The data of 24 patients under 18 years of age with a histologic diagnosis of ES/PNET in the chest wall that received RT in our department between February 2003 and July 2020 were retrospectively evaluated. RT was applied to the primary site±whole involved chest wall and to the whole lung in patients with lung metastasis. RESULTS: The median age was 8.5 years (range: 1.5 to 17 y), 15 (63%) patients were female and 9 were male (37%). The tumor localization was extrathoracic in 18 (75%) and intrathoracic in 6 (25%) patients. Mediastinal lymph node and distant metastasis (DM) was present in 5 (21%) and 4 (16%) cases at diagnosis, respectively. The median follow-up after RT was 47 months (range: 11 to 162 mo). The 2-year and 5-year overall survival, event-free survival, local recurrence-free survival, and pleural recurrence-free survival were 83% and 48%, 48% and 42%, 74% and 48%, and 61% and 52%, respectively. The overall local control rate was 83% and the pleural control rate was 67%. RT was well tolerated, with 1 case of grade 3 acute dermatitis and 1 case of grade 3 subacute radiation pneumonitis. Late toxicity was observed in 3 (13%) cases. CONCLUSION: Long-term survival can be achieved with extended-field RT even in patients with ES/PNET of the chest wall with DM. The low toxicity rates allow us to draw the conclusion that RT with modern techniques is an effective and safe treatment modality for these patients.

Anaplastic large cell lymphoma with ALK::ATIC fusion mimicking a histiocytic sarcoma debuting as an anterior thoracic soft tissue tumor with exceptional clinicopathological, morphological and molecular features.

A 56-year-old woman debuted with a palpable painless mass in the anterior thorax wall at the level of the second and third right parasternal intercostal space, which progressively increased in size over 5 months accompanied by localized skin rash, mild dyspnea and chest pain when changing position. Imaging studies showed a soft tissue mass measuring 75 × 62 mm and a density of 34 Hounsfield Units that had caused the lysis of the costal arches and grew expansively towards the anterior mediastinum, without identifying mediastinal adenopathies only by this imaging method. Core biopsy was performed, which was initially diagnosed as histiocytic sarcoma (HS); however, when the diagnostic panel was expanded to include molecular and NGS studies, the final diagnosis was anaplastic large cell lymphoma with ALK::ATIC fusion. Here, we report a very rare neoplasm with unusual clinical presentation, histopathology and molecular features.

The application of three-dimensional custom-made prostheses in chest wall reconstruction after oncologic sternal resection.

BACKGROUND AND OBJECTIVES: As one of the cutting-edge advances in the field of reconstruction, three-dimensional (3D) printing technology has been constantly being attempted to assist in the reconstruction of complicated large chest wall defects. However, there is little literature assessing the treatment outcomes of 3D printed prostheses for chest wall reconstruction. This study aimed to analyze the surgical outcomes of 3D custom-made prostheses for the reconstruction of oncologic sternal defects and to share our experience in the surgical management of these rare and complex cases. METHODS: We summarized the clinical features of the sternal tumor in our center, described the surgical techniques of the application of 3D customized prosthesis for chest wall reconstruction, and analyzed the perioperative characteristics, complications, overall survival (OS), and recurrence-free survival of patients. RESULTS: Thirty-two patients with the sternal tumor who underwent chest wall resection were identified, among which 13 patients used 3D custom-made titanium implants and 13 patients used titanium mesh for sternal reconstruction. 22 cases were malignant, and chondrosarcoma is the most common type. The mean age was 46.9 years, and 53% (17/32) of the patients were male. The average size of tumor was 6.4 cm, and the mean defect area was 76.4 cm2. 97% (31/32) patients received R0 resection. Complications were observed in 29% (9/32) of patients, of which wound infection (22%, 7/32) was the most common. The OS of the patients was 72% at 5 years. CONCLUSION: We demonstrated that with careful preoperative assessment, 3D customized prostheses could be a viable alternative for complex sternal reconstruction.

An aggressive case of a thoracic undifferentiated SMARCA4-deficient tumor with extensive pleural involvement.

SMARCA4-deficient undifferentiated thoracic tumors are a rare phenomenon. A 40-year-old male was newly diagnosed with SMARCA4-deficient undifferentiated non-small cell lung cancer. He had a history of heavy smoking and job-related exposure to metal dust and melted nickel. CT imaging showed numerous right-sided pleural masses and soft tissue plaques, but no metastases. CT-guided biopsy of a pleural mass confirmed the diagnosis. He was prescribed six cycles of carboplatin paclitaxel, and follow-up imaging showed largely stable disease. Treatment was changed to nivolumab due to shortness of breath, and he received one cycle of nivolumab without considerable side effects. Unfortunately, during the second cycle of his nivolumab, the patient presented with new weakness. Imaging showed spinal cord metastasis and he underwent a laminectomy; he was subsequently followed up as an outpatient. The objective of this publication was to explore SMARCA4-deficient undifferentiated thoracic tumors, other related SMARCA4-deficient tumors, and their overall pattern of presentation. The genetic aberrations of this case are compared to recent publications that also discuss genetic aberrations commonly occurring with this disease process, with an ultimate goal of hastening detection and adding to the library of treatment results.

All That Is Small Is Not a Small-Cell Carcinoma: Thoracic SMARCA4-Deficient Undifferentiated Tumors Masquerading as SCLC.

Small-cell lung carcinoma (SCLC) cell lines have been widely utilized as a preclinical model of this highly aggressive disease. However, since their creation decades ago, novel tumor entities have been defined that might clinicopathologically mimic SCLC, which notably includes thoracic SMARCA4-deficient undifferentiated tumor (SMARCA4-UT). Multiomic reassessment of the presumed SCLC cell lines with high YAP1 expression reveals that nearly all of these tumors represent unsuspected SMARCA4-UT. See related article by Ng et al., p. 1846.

[Cytopathological characteristics of SMARCA4-deficient thoracic undifferentiated tumors in serous effusion].

Objective: To investigate the clinicopathological characteristics of SMARCA4-deficient thoracic undifferentiated tumors, and the diagnostic value of the cells in serous effusion. Methods: Eleven cases of SMARCA4-deficient tumor were collected from the Affiliated Hospital of Hebei University, China from January 2018 to July 2023, which were diagnosed using cell block of serous effusion. The clinical, histopathological, immunohistochemical and molecular genetic features were reviewed, along with related literature. Results: All the 11 patients were males with ages ranging from 54 to 77 years (median 64 years). Nine patients were smokers and two had an unknown smoking history. Most of them complained of cough and dyspnea with pleural effusion. The primary tumor sites included lung (9 cases), thoracic wall (1 case), and mediastinum (1 case), while 3 patients had a history of lung surgery. Histologically, tumor cells were large and pleomorphic, with increased nuclear-cytoplasmic ratio. They also showed round nuclei, conspicuous nucleoli, and basophilic cytoplasm in serous effusion. Immunohistochemically, tumor cells in all cases were negative for SMARCA4/BRG1, CKpan and CK7, but positive for SMARCB1/INI1. Some of the cases were positive for CD34 (7/11), synaptophysin (4/11) and SALL4 (2/11). Histologically, monotonous tumor cells formed solid sheets or anastomosing islands with poor cell adhesion and rhabdoid morphology. Brisk mitotic figures were accompanied by large areas of necrosis. Some cases focally exhibited syncytia, and some had bright cytoplasm and vesicular chromatin. The immunohistochemical profiles in the tumor tissues were consistent with those of cytology. Six cases were negative for PD-L1 (22c3). Among the 6 cases analyzed by targeted next generation sequencing, concurrent SMARCA4 and TP53 mutations were detected in all 6 cases. Some of the 6 tumors showed mutations of STK11, CDKN2A, and MET, and amplification of ERBB2, exon deletion of BRCA2, etc. Follow-up information was available in all cases and ranged from 2 to 24 months. The patients showed metastases to various sites, including lymph node, liver, kidney, adrenal gland, brain, bone and other sites. Four patients died of the tumor. The survival time of 4 patients who underwent radical resection or radiofrequency ablation was more than 13 months. Conclusions: SMARCA4-deficient thoracic sarcoma is a rare but highly aggressive tumor with dismal prognosis and rhabdomyoid features. It is difficult to diagnose this disease using only serous effusion samples. This tumor thus warrants careful consideration. Accurate diagnosis can greatly improve early diagnosis and treatment of these tumors.

Under the Microscope: A Case Report of Thoracic SMARCA4-Deficient Undifferentiated Tumor with Review of the Literature.

OBJECTIVE: SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) is a highly malignant neoplasm with an undifferentiated or rhabdoid phenotype, posing a diagnostic challenge. This case report aims to create awareness about this rare neoplasm while dealing with cases presenting with undifferentiated morphology. CASE REPORT: A 55-year-old gentleman with constitutional symptoms and lymphadenopathy. Imaging revealed a mass lesion in the right upper lobe of the lung. A biopsy of the cervical lymph node showed diffusely effaced architecture replaced by sheets of undifferentiated pleomorphic cells with vesicular nuclei, prominent nucleoli, eosinophilic cytoplasm, and multiple necrotic foci. An extensive immunohistochemistry (IHC) panel was applied, which showed positivity for synaptophysin, vimentin, and focal CD34 and EMA expression. Other markers like pan-cytokeratin, p40, TTF1, CD56, INSM1, calretinin, CD45, SOX10, S100, CD30, CD117, SMA, and Desmin were negative, with INI1 retained. The IHC panel excluded the morphological differentials of carcinoma, lymphoma, rhabdomyosarcoma, melanoma, and germ cell tumor. Further literature review led to the possibility of the SMARCA4-UT entity, which had a morphology and IHC profile similar to the present case. Testing for SMARCA4 (BRG-1) by IHC showed a complete loss in the tumor cells, favoring the diagnosis of Thoracic SMARCA4-deficient undifferentiated tumor (SMARCA4-UT). CONCLUSION: SMARCA4-UTs are rare, highly aggressive, and poorly differentiated thoracic tumors. Recognizing them is vital as there is potential for therapeutic interventions such as immunotherapy and SMARCA4-targeted therapies, offering promising prospects for the future.

Diagnostic yield of endobronchial ultrasound and virtual CT navigational bronchoscopy for biopsy of pulmonary nodules, mediastinal lymph nodes, and thoracic tumors in children.

OBJECTIVE: Endobronchial ultrasound-guided transbronchial biopsy and needle aspiration (EBUS-TBB/EBUS-TBNA) are first line investigative modalities for lung and mediastinal pathology in adults. We aimed to characterize and assess the diagnostic yield of EBUS and virtual CT navigation guided biopsies in children. STUDY DESIGN: This single center, retrospective cohort study included patients who underwent radial or linear EBUS procedures (+/- CT navigation) for biopsy of mediastinal lymph nodes, tumors, and pulmonary nodules. Demographic, procedural, and outcome were collected. RESULTS: Sixty procedures were performed in 56 patients aged 2-22 years of age between January 2015 and May 2023. The most common indications for biopsy were pulmonary nodules (45%) and hilar/mediastinal lymphadenopathy (33%). For cases in which a final diagnosis was ascertained by any means, the diagnostic yield for linear EBUS (mediastinal pathology) was 76% and the diagnostic yield from radial EBUS (pulmonary nodules and lung masses) was 85%. The most common diagnoses were infection (45%), malignancy (17%), and sarcoidosis (11%). Among patients in whom infection was the final diagnosis, a total of 31 pathogens were identified. Eighteen were identified on bronchoalveolar lavage and an additional 14 pathogens identified on EBUS-TBB, representing an increase of 77% (p < .005). The sensitivity, specificity, negative and positive predictive values for malignancy detection were 73%, 100%, 94%, and 100%, respectively. CONCLUSION: EBUS-TBB/TBNA is a safe and effective way to diagnose lung and mediastinal pathology in children. Pediatric interventional pulmonology is a growing field offering minimally-invasive diagnostic opportunities for children in whom more invasive procedures were previously the only option.

Thoracic SMARCA4-deficient undifferentiated tumor: current knowledge and future perspectives.

Thoracic SMARCA4-deficient undifferentiated tumor is a newly recognized disease entity characterized as a high-grade malignant neoplasm with an undifferentiated or rhabdoid phenotype. The tumor was initially identified as a subtype of thoracic sarcoma with SMARCA4 loss, but further investigation resulted in its classification as a subtype of epithelial malignancies in the current World Health Organization classification. SMARCA4-deficient undifferentiated tumor is highly aggressive and has a poor prognosis. Because of its rarity, an optimal treatment strategy has not yet been identified. In this review, we summarize the literature on SMARCA4-deficient undifferentiated tumor in terms of its clinical characteristics, diagnosis, treatment strategy and future perspectives.

Malignant Chest Wall Tumors: Complex Defects and Their Management-A Review of 181 Cases.

BACKGROUND: Chest wall tumors are a heterogeneous group of tumors that are managed by surgeons from diverse specialties. Due to their rarity, there is no consensus on their diagnosis and management. MATERIALS: This retrospective, descriptive analysis includes patients with malignant chest wall tumors undergoing chest wall resection. Tumors were classified as primary, secondary, and metastatic tumors. The analysis includes clinicopathological characteristics, resection-reconstruction profile, and relapse patterns. RESULTS: A total of 181 patients underwent chest wall resection between 1999 and 2020. In primary tumors (69%), the majority were soft tissue tumors (59%). In secondary tumors, the majority were from the breast (45%) and lung (42%). Twenty-five percent of patients received neoadjuvant chemotherapy, and 98% of patients underwent R0 resection. Soft tissue, skeletal + soft tissue, and extended resections were performed in 45%, 70%, and 28% of patients, respectively. The majority of patients (60%) underwent rib resections, and a median of 3.5 ribs were resected. The mean defect size was 24 cm2. Soft tissue reconstruction was performed in 40% of patients, mostly with latissimus dorsi flaps. Rigid reconstruction was performed in 57% of patients, and 18% underwent mesh-bone cement sandwich technique reconstruction. Adjuvant radiotherapy and chemotherapy were given to 29% and 39% of patients, respectively. CONCLUSIONS: This is one of the largest single-institutional experiences on malignant chest wall tumors. The results highlight varied tumor spectra and multimodality approaches for optimal functional and survival outcomes. In limited resource setting, surgery, including reconstructive expertise, is very crucial.

NUT carcinoma and thoracic SMARCA4-deficient undifferentiated tumour: facts and controversies.

NUT carcinoma and thoracic SMARCA4-deficient undifferentiated tumour are unique entities in the 5th edition of the World Health Organisation (WHO) Classification of Thoracic Tumours, whose definitions include molecular genetic abnormalities. These aggressive tumours require rapid work-ups on biopsies, but a broad list of differential diagnoses poses challenges for practising pathologists. This review provides an update on their key clinicopathological and molecular characteristics, as well as controversies regarding tumour classification and diagnostic strategy. Phenotypical assessment plays a substantial role in diagnosis because recurrent and predictable clinicopathological findings exist, including robust immunohistochemical phenotypes. Accurate diagnosis is crucial for appropriate management and a clearer understanding of the disease.

[Feasibility of cardiac surgical techniques for intrathoracic tumors]. / O tselesoobraznosti ispol'zovaniya kardiokhirurgicheskikh tekhnologii pri vnutrigrudnykh opukholyakh.

OBJECTIVE: To analyse safety and expediency of cardiac surgical technologies including cardiopulmonary bypass (CPB) in patients with locally advanced lung cancer and invasive tumors of the mediastinum. MATERIAL AND METHODS: Cardiac surgical techniques and CPB were used in 23 patients (group 1) with locally advanced thoracic tumors between 2005 and 2015. For the same period, there were 22 patients (group 2) who underwent combined surgeries and could have had similar techniques. However, these techniques were not used for various reasons. Mediastinal malignancies and non-small cell lung cancer were diagnosed in 26 (57.8%) and 19 (42.2%) patients, respectively. Invasion of superior vena cava (n=15), aorta (n=13) and pulmonary artery (n=12) was the most common. Lesion of innominate vein (n=8), left atrium (n=6) and innominate artery (n=4) was less common. A total of 21 pneumonectomies were performed (14 in the first group and 7 in the second group). Lobectomy was less common (one patient in each group). Sublobar lung resection was performed in 10 patients (2 patients in the first group and 8 ones in the second group). All resections were total in the first group (R0) that was confirmed by routine morphological examination of resection margins of different organs and vessels. The situation was worse in the second group (R1 in 19 (86.4%) patients, R2 in 3 (13.6%) patients). RESULTS: Total postoperative morbidity was 53.3%, mortality - 8.2%. These values are higher compared to patients undergoing surgical treatment for thoracic malignancies. Incidence of postoperative complications was higher in the first group (16 (69.6%) and 8 (36.4%), respectively). Four patients died in the first group. Sepsis (n=2), acute right ventricular failure (n=1) and acute myocardial infarction (n=1) caused death. There were no lethal outcomes in the second group. Various postoperative complications were diagnosed only in 8 (36.4%) patients. The long-term results were followed-up in 80% of patients. In the first group, 3- and 5-year survival rates were 30.5% and 25%, respectively (median 43.8 months). In the second group, these values were 25% and 2%, respectively (median 24.9 months). Long-term mortality in the second group was caused by progression of malignant process, including local recurrence, after palliative surgery (R1, R2 resection). CONCLUSION: Higher risk of postoperative complications and mortality in patients undergoing on-pump surgery is compensated by significantly better long-term results. Further progress is associated with higher safety of CPB, as well as solving some organizational and educational problems.

Diagnosis of thoracic SMARCA4-deficient undifferentiated tumor in cytology.

INTRODUCTION: Although alterations in SMARCA4-deficient occur in non-small cell lung carcinoma (SD-NSCLC), thoracic SMARCA4-deficient undifferentiated tumor (TSDUT) is recognized as a distinct entity in the 2021 World Health Organization Classification of Thoracic Tumors because of unique morphologic, immunophenotypic and molecular features, and worse survival compared with SD-NSCLC. Cytologic diagnosis of TSDUT is clinically important because of its aggressive behavior and because it is often diagnosed by fine-needle aspiration because TSDUTs are usually unresectable at presentation. Here, we identify cytologic features that can be used for recognition of TSDUT and distinction from SD-NSCLC. MATERIALS AND METHODS: Cytomorphologic features were investigated in cytology specimens from patients with TSDUT (n = 11) and compared with a control group of patients with SD-NSCLC (n = 20). RESULTS: The presence of classic rhabdoid morphology, at least focally, was entirely specific for TSDUT (n = 6, 55%) compared with SD-NSCLC (n = 0) in this study. TSDUT more frequently showed tumor necrosis (n = 11, 100% vs. n = 8, 40%; p = .001), dominant single-cell pattern on aspirate smears or touch preparation slides (n = 8 [of 9], 80% vs. n = 3, 15%; p = .010), nuclear molding (n = 5, 45% vs. n = 1, 5%; p = .013), and indistinct cell borders (n = 11, 100% vs. n = 5, 25%; P < .001) compared with SD-NSCLC, respectively. CONCLUSIONS: Cytomorphologic features occurring more frequently in TSDUT include tumor necrosis, dominant single-cell pattern, nuclear molding indistinct cell borders, and focal rhabdoid cells. Presence of these features in a cytology specimen of an undifferentiated tumor, particularly in a patient with a thoracic mass, should raise suspicion for TSDUT and prompt appropriate ancillary workup.

Cord Herniation through the Site of Undiagnosed Thoracic Dermoid Tumour during Spinal Anaesthesia; Report of a Case and Describing Ways to Avoid.

Spinal anaesthesia (SA) is one of the most prevalent types of anaesthetic procedures. There are very few reports of cord herniation through the site of spinal canal stenosis due to tumour. A 33-year-old female presented with acute paraparesis after spinal anaesthesia for caesarean section. Magnetic resonance imaging (MRI) revealed an intradural mass from posterior of T6 to T8-T9 interface. We operated the patient and after laminectomy of T6 to T9, dermoid tumour containing hairs was totally resected and cord was completely decompressed. After 6 months, the patient is without any neurological deficit. Puncturing the dura with cerebrospinal fluid (CSF) in the presence of an extramedullary mass could cause cord herniation through the blockade. In these cases, awareness about related signs even in absence of symptoms or complaints could help us to prevent post-SA neurological deficit.

[Thoracic SMARCA4-deficient undifferentiated tumor-pathological diagnosis and combined immune checkpoint inhibitor treatment].

We explored clinicopathological features and treatment strategies for thoracic SMARCA4-deficient undifferentiated tumor (SMARCA4-UT). Thoracic SMARCA4-UT is a new entity recently acknowledged in the 2021 edition of World Health Organization Classification of Thoracic Tumors, and doctors are relatively unfamiliar with its diagnosis, treatment, and prognosis. Taking a case of SMARCA4-UT treated in Peking University First Hospital as an example, this multi-disciplinary discussion covered several hot issues on diagnosing and treating thoracic SMARCA4-UT, including histological features, immu- nohistochemical and molecular phenotype, immune checkpoint inhibitor (ICI) therapy, and pathological assessment of neoadjuvant therapy response. The patient was an older man with a long history of smoking and was admitted due to a rapidly progressing solid tumor in the lower lobe of the right lung. Histologically, tumor cells were epithelioid, undifferentiated, diffusely positive for CD34, and partially positive for SALL4.The expression of BRG1 protein encoded by SMARCA4 gene was lost in all of tumor cells, and next-generation sequencing(NGS)confirmed SMARCA4 gene mutation (c.2196T>G, p.Y732Ter). The pathological diagnosis reached as thoracic SMARCA4-UT, and the preoperative TNM stage was T1N2M0 (ⅢA). Tumor proportion score (TPS) detected by immunohistochemistry of programmed cell death 1-ligand 1 (PD-L1, clone SP263) was 2%. Tumor mutation burden (TMB) detected by NGS of 1 021 genes was 16. 3/Mb. Microsatellite detection showed the tumor was microsatellite stable (MSS). Neo-adjuvant therapy was implemented with the combined regimen of chemotherapy and ICI. Right lower lobectomy was performed through thoracoscopy after the two weeks' neoadjuvant. The pathologic assessment of lung tumor specimens after neoadjuvant therapy revealed a complete pathological response (CPR). The post-neoadjuvant tumor TNM stage was ypT0N0M0. Then, five cycles of adjuvant therapy were completed. Until October 2022, neither tumor recurrence nor metastasis was detected, and minimal residual disease (MRD) detection was negative. At present, it is believed that if BRG1 immunohistochemical staining is negative, regardless of whether SMARCA4 gene mutation is detected, it should be classified as SMARCA4-deficient tumors. SMARCA4-deficient tumors include a variety of carcinomas and sarcomas. The essential criteria for diagnosing SMARCA4-UT includes loss of BRG1 expression, speci-fic histological morphology, and exclude other common thoracic malignant tumors with SMARCA4-deficiency, such as squamous cell carcinoma, adenocarcinoma and large cell carcinoma. SMARCA4-UT is a very aggressive malignant tumor with a poor prognosis. It has almost no targeted therapy mutations, and little response to chemotherapy, but ICI is currently the only effective drug. The successful diagnosis and treatment for this case of SMARCA4-UT should enlighten significance for various kinds of SMARCA4-deficient tumors.