A Rare Case of Thoracic SMARCA4-Deficient Undifferentiated Tumor With Diffuse Brain Metastasis.

Thoracic SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) is a recently described rare and aggressive malignancy characterized by undifferentiated cell morphology and the loss of the Brahma-related gene 1 (BRG1) protein. Its pathogenesis involves mutational loss of SMARCA4 gene expression, which encodes the BRG1 protein that serves as one of the catalytic subunits of the SWItch/Sucrose Non-Fermentable (SWI/SNF) chromatin remodeling complex. This malignancy of the thorax predominantly affects middle-aged male smokers and commonly metastasizes to lymph nodes, bones, adrenal glands, liver, gastrointestinal tract, central nervous system, and kidney. Cases of brain metastasis have been reported but are less common. We report a case of this tumor initially presenting with diffuse brain metastasis in a 55-year-old male with a significant smoking history. We reviewed the current literature on the diagnostic and therapeutic challenges posed by this highly aggressive thoracic tumor.

Delayed Diagnosis of SMARCA4-Deficient Undifferentiated Tumor in a Heavy Smoker Male Patient: Discovered Through Bone Sampling, with Extensive Distant Metastases and Concurrent Granulomatous Disease, Leading to Patient Fatality.

Background. SMARCA4-deficient undifferentiated tumors are rare and pose a diagnostic challenge. This study delves into the intricate diagnostic terrain of SMARCA4-deficient undifferentiated tumors, providing insights into their diverse clinical presentations and diagnostic approaches. Case Presentation. A 69-year-old heavy-smoker man with adalimumab-treated rheumatoid arthritis presented with multiple lesions. A CT scan revealed a spiculated lung mass, enlarged mediastinal lymph nodes, and hepatic lesions. A whole-body FDG-PET/CT scan revealed heterogeneous hypermetabolic lesions in the lung, liver, and bone. Initial two core needle liver biopsies and a left upper lobe lung wedge resection initially indicated steatohepatitis and granulomatous formation with no evidence of malignancy. Several months later, the patient returned with left-sided flank pain and significant weight loss. CT scan identified a thigh mass, adrenal lesion, and extensive multiple skeletal lesions. A biopsy of the thigh mass revealed an extensively necrotic, epithelioid-to-spindled cell neoplasm with positive staining for pan keratin, focal staining for CD56, and a loss of nuclear expression of SMARCA4. A final diagnosis of SMARCA4-deficient undifferentiated tumor was rendered. Unfortunately, the patient's condition deteriorated, and he died a few weeks after receiving the final diagnosis. Conclusion. SMARCA4-deficient undifferentiated tumors have emerged as recent subjects of medical study, distinguished by their unique morphology and SMARCA4-deficient immunohistochemistry. These tumors present diverse clinical manifestations, affecting multiple organ systems. This report underscores the diagnostic complexities associated with complex clinical presentation and highlights the importance of multidisciplinary collaboration in addressing challenging clinical scenarios, particularly among heavy smoker male patients and intricate radiological presentations.

Gastric SMARCA4-deficient undifferentiated tumor (SMARCA4-UT): a clinicopathological analysis of four rare cases.

BACKGROUND: SMARCA4, as one of the subunits of the SWI/SNF chromatin remodeling complex, drives SMARCA4-deficient tumors. Gastric SMARCA4-deficient tumors may include gastric SMARCA4-deficient carcinoma and gastric SMARCA4-deficient undifferentiated tumor (SMARCA4-UT). Gastric SMARCA4-UT is rare and challenging to diagnose in clinical practice. The present report aims to provide insight into the clinicopathological characteristics and genetic alterations of gastric SMARCA4-UTs. RESULTS: We retrospectively reported four rare cases of gastric SMARCA4-UTs. All four cases were male, aged between 61 and 82 years. These tumors presented as ulcerated and transmural masses with infiltration, staged as TNM IV in cases 1, 2 and 4, and TNM IIIA in case 3. Pathologically, four cases presented solid architecture with undifferentiated morphology. Cases 2 and 3 showed focal necrosis and focal rhabdoid morphology. Immunohistochemical staining showed negative expression of epithelial markers and deficient expression of SMARCA4. Furthermore, positivity for Syn (cases 1, 2 and 3) and SALL4 (cases 1 and 2) were observed. Mutant p53 expression occurred in four cases, resulting in strong and diffuse staining of p53 expression in cases 1, 2 and 4, and complete loss in case 3. The Ki67 proliferative index exceeded 80%. 25% (1/4, case 4) of cases had mismatch repair deficiency (dMMR). Two available cases (cases 1 and 3) were detected with SMRACA4 gene alterations. The response to neoadjuvant therapy was ineffective in case 1. CONCLUSIONS: Gastric SMARCA4-UT is a rare entity of gastric cancer with a poor prognosis, predominantly occurs in male patients. The tumors are typically diagnosed at advanced stages and shows a solid architecture with undifferentiated morphology. Negative expression of epithelial markers and complete loss of SMARCA4 immunoexpression are emerging as a useful diagnostic tool for rare gastric SMARCA4-UTs.

SMARCA4-deficient central nervous system metastases: A case series and systematic review.

SMARCA4 alterations can be encountered in a variety of human neoplasms, and metastases to the central nervous system (CNS) are rare, offering a challenge to neuropathologists despite not representing a distinct diagnostic entity. To better understand the clinical and histologic presentation of such neoplasms, we report an observational case series and systematic review of 178 unique articles that yielded 15 published cases and 7 cases from institutional files. In the systematic review, the median age was 58 years, the male-to-female ratio was 2:1, and the most common diagnosis was lung adenocarcinoma; all CNS metastases were discovered within 1 year of presentation. In the case series, the median age was 58 years, the male-to-female ratio was 6:1, and all known metastases originated from the lung. Most patients had a smoking history and died of disease. GATA-3 positivity was seen in most case series examples. Concurrent TP53 mutations (83.3%) and a high tumor mutation rate (60%) were common. To our knowledge, this is the only case series and systematic review in the English literature aimed at assessing SMARCA4-altered metastases in the CNS and vertebral column. We highlight the challenges of neuropathologic evaluation of such tumors and provide observational evidence of early metastases, histologic appearances, and immunohistochemical findings, including previously unreported GATA-3 positivity.

Molecular and Treatment Characteristics of SMARCB1 or SMARCA4-Deficient Undifferentiated Tumor: Retrospective Case Series.

SMARCB1 or SMARCA4-deficient sinonasal carcinoma or thoracic undifferentiated tumor has aggressive nature with a poor prognosis. Patients with this disease were diagnosed by immunohistochemistry or next-generation sequencing. Those who were able to receive a surgery tended to be cured, while the others treated with chemotherapy, radiation therapy, or immune checkpoint inhibitor were often insensitive to these therapies. However, one having CD274 (PD-L1) amplification showed the response to immune checkpoint inhibitor and a good prognosis. We believed that this report could provide promising information for determining the optimal treatment option.

Thoracic SMARCA4-deficient tumors: a clinicopathological analysis of 52 cases with SMARCA4-deficient non-small cell lung cancer and 20 cases with thoracic SMARCA4-deficient undifferentiated tumor.

Background: Thoracic SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) is a distinct clinicopathological entity with an aggressive clinical course. Additionally, SMARCA4/BRG1 deficiency can be observed in a few patients with non-small cell lung cancer (NSCLC). We aimed to compare the clinicopathological, immunohistochemical and prognostic features of SMARCA4-deficient NSCLC (SMARCA4-dNSCLC) with those of thoracic SMARCA4-UT. Methods: Patients with BRG1-deficient tumors in the lung or thorax were enrolled in the study from the Department of Pathology of West China Hospital, Sichuan University, from January 2014 to June 2022. We retrospectively collected the clinicopathological and immunohistochemical features and outcomes of these patients. Results: Seventy-two patients had tumors in the lung or thorax with BRG1-deficient expression, including 52 patients with SMARCA4-dNSCLC and 20 patients with thoracic SMARCA4-UT. Among the patients with SMARCA4-dNSCLC, 98.1% were male, 85.7% were smokers, and 79.5% (35/44) had tumor-node-metas-tasis (TNM) III-IV tumors. Among the patients with thoracic SMARCA4-UT, all were males who smoked, and 93.75% (15/16) had TNM III-IV tumors. Pure solid architecture and necrosis were the predominant pathological features. Rhabdoid morphology was observed in some SMARCA4-dNSCLCs (10/52, 19.2%) and thoracic SMARCA4-UTs (11/20, 55%). In most patients with thoracic SMARCA4-UT, the tumors exhibited scattered weak expression or negative expression of epithelial markers, and positive expression of CD34 and Syn. Overall survival (OS) and progression-free survival (PFS) were not significantly different between patients with SMARCA4-dNSCLC and patients with thoracic SMARCA4-UT (p = 0.63 and p = 0.20, respectively). Conclusions: Thoracic SMARCA4-DTs include SMARCA4-dNSCLC and thoracic SMARCA4-UT. Both have overlapping clinicopathological features and poor prognosis. We hypothesize that thoracic SMARCA4-UT may be the undifferentiated or dedifferentiated form of SMARCA4-dNSCLC. However, further studies with larger cohorts and longer follow-up periods are needed.

Thoracic SMARCA4-deficient undifferentiated tumor: A clinicopathological and prognostic analysis of 35 cases and immunotherapy efficacy.

BACKGROUND: Thoracic SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) is a recently recognized distinct clinicopathological entity according to the fifth edition of the 2021 World Health Organization Classification (WHO) for thoracic tumors. Thoracic SMARCA4-UTs are diagnostically challenging to diagnose, especially on small biopsies. METHODS: We identified 35 thoracic SMARCA4-UTs from the Department of Pathology of West China Hospital, Sichuan University, between January 2017 and December 2022. In the present study, we summarized the clinicopathological features, prognostic significance and immunotherapy efficacy of thoracic SMARCA4-UTs. RESULTS: All 35 patients were male, and 88.6 % were smokers. The left upper lobe (25.7 %) and mediastinum (20.0 %) were the most affected sites. 17.1 % of the patients received surgical treatment. 30.4 % of the patients were stage III, and 69.6 % were stage IV. Solid architecture (100 %), rhabdoid morphology (51.4 %) and necrosis (42.9 %) were the common histological features. Immunohistochemical staining revealed CD34 and synaptophysin positivity in most patients (76.9 % and 65.2 %, respectively). Patients had unfavorable outcomes. Patients who received immunotherapy had better OS and PFS than those who did not (p = 0.007 and p = 0.02, respectively). Five patients were evaluated for immunotherapy efficacy, and four of those patients were negative expression of PD-L1. Cases 1-4 presented TIL counts ranging from 20 to 1000/HPF. Case 5 presented TIL counts of 5-10/HPF. Mutations in SMARCA4 were confirmed in cases 4 and 5, and the TMB was 5.98 and 5.03 mutations/Mb, respectively. Case 1 achieved a CR, cases 2-4 achieved a PR, and case 5 had a PD. Five patients who received immunotherapy were all alive, with OS ranging from 10.7 to 33.6 months. CONCLUSIONS: Thoracic SMARCA4-UTs exhibited an aggressive clinical course, presented solid architecture with or without necrosis and/or rhabdoid morphology, and frequently expressed CD34 and synaptophysin. Some thoracic SMARCA4-UTs appear to be associated with responsiveness to immunotherapy, suggesting the need for validation in larger series.

SMARCA4-deficient tumors in the adrenal gland and small intestines: A rare case report.

Thoracic SMARCA4-deficient undifferentiated tumors (SMARCA4-UTs) are rare undifferentiated thoracic malignancies with poor prognosis. They predominantly affect young men who are heavy smokers. Recently, the category of SMARCA4-deficiency-related malignancy has been expanded to include extra-thoracic sites, such as the paranasal sinuses, gastrointestinal tract, ovary, and uterus. We report a rare case of SMARCA4-deficient tumors in the adrenal gland and small intestines. SMARCA4-deficient tumors should be included in the differential diagnosis when multiple large masses with heterogeneous contrast effect and strong accumulation are seen in cancers of unknown primary on 18F-fluorodeoxyglucose (FDG) positron emission tomography with computed tomography (PET/CT).

Clinicopathological characteristics and treatment outcomes of advanced SMARCA4-deficient thoracic tumors.

PURPOSE: SMARCA4-deficient thoracic tumors, characterized by distinct clinicopathological, morphological, immunohistochemical, and genetic features, differ significantly from conventional non-small-cell lung carcinomas (NSCLCs). This group encompasses both SMARCA4-deficient NSCLCs (SMARCA4-NSCLCs) and SMARCA4-deficient undifferentiated tumors (SMARCA4-UTs). The efficacy of PD-1 inhibitors in treating SMARCA4-deficient thoracic tumors remains uncertain. METHODS: Medical records of 36 patients diagnosed with stage IIIB, IIIC, or IV SMARCA4-deficient thoracic tumors were analyzed. We assessed the clinical, pathological, and genetic features of these patients through immunohistochemistry (IHC) and a 68-gene panel next-generation sequencing (NGS). We compared the differences between SMARCA4-NSCLCs and SMARCA4-UTs, and evaluated the impact of chemotherapy and immunotherapy on patient outcomes. RESULTS: The majority of patients with SMARCA4-deficient thoracic tumors were heavy-smoking males, averaging 64.6 years in age. IHC predominantly showed weak or negative staining for markers such as TTF-1, CK5/6, p40, synaptophysin, chromogranin A, and CD56, which are often associated with adenocarcinoma, squamous cell carcinoma, and neuroendocrine tumors. The most common genetic mutations identified via NGS included TP53, CDKN2A, KRAS, STK11, NF1, and PTEN. No significant overall survival (OS) difference was observed between SMARCA4-NSCLCs and SMARCA4-UTs (p = 0.366). The median OS for patients treated with chemotherapy (n = 9) was 447 days, while the median OS for patients undergoing PD-1-inhibitor-based therapy (n = 16) was not reached (p = 0.105). CONCLUSION: SMARCA4-deficient thoracic tumors exhibit distinct characteristics from conventional NSCLCs, and PD-1 inhibitors show promise in treating advanced SMARCA4-deficient thoracic tumors.

Diagnosis of a SMARCA4-deficient undifferentiated tumor using multigene panel testing: A case report.

Key Clinical Message: SMARCA4-deficient thoracic carcinoma is a malignant tumor that may present as cancer of unknown primary. This tumor is refractory and requires a novel approach. In addition to identifying therapeutic targets, multigene panel testing can reveal novel genetic mutations, leading to more pathologically relevant diagnoses and appropriate tumor care. Abstract: SMARCA4-deficient undifferentiated tumors are characterized by SMARCA4 inactivation. We present a case of a 74-year-old man with an undifferentiated tumor and a novel SMARCA4 mutation detected using multigene panel testing. The tumor was multiagent and refractory to three chemotherapy lines. The test results helped guide appropriate medical management.

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.

Thoracic SMARCA4-deficient undifferentiated tumor with associated granulomatous reaction and response to pembrolizumab.

Thoracic SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) is a rare entity that was recently described in the current World Health Organization Classification of Tumors. These lesions are highly aggressive with dismal prognosis, and most patients present with metastasis at the time of diagnosis. While there are about 100 cases of SMARCA4-UT described in the literature, there are only few existing reports that describe the cytomorphology of these lesions. We present a patient with masses involving the mediastinum, right lung, right supraclavicular lymph node and right adrenal gland. Subsequent core-needle biopsy of the right supraclavicular lymph node showed epithelioid to pleomorphic tumor cells with prominent nucleoli and associated granulomatous inflammation. The tumor cells were positive for CD34 and synaptophysin, and were negative for cytokeratins. SMARCA4 and SMARCA2 both showed loss of expression, which led to the diagnosis of SMARCA4-UT. The patient underwent treatment with pembrolizumab (PD-1 blocker), carboplatin, etoposide, and radiotherapy, resulting in an almost 55% reduction in the size of the primary tumor. Our case illustrates that an associated granulomatous inflammation might be an uncommon presentation of an already rare malignancy, and awareness of this phenomenon would prevent from mistaking SMARCA4-UT for other more well-known entities that can present with granulomas.

SMARCA4-deficient undifferentiated thoracic tumor: A case report.

BACKGROUND: SMARCA4-deficient undifferentiated tumors (SMARCA4-DUTs) present with diverse clinical manifestations and progress to metastasis and even cause death within a few months. This novel subset of undifferentiated tumors occurs in the middle-aged population and is strongly associated with a smoking history. Distinguishing it from other malignancies is challenging. CASE SUMMARY: A 62-year-old man presented with chest pain for 7 d. The patient had no respiratory symptoms and normal pulmonary function test results. The patient had been a smoker for 8 years and quit smoking 2 years ago. Chest computed tomography revealed a huge mass involving the left upper and lower lung lobes with pericardial invasion and multiple metastases. Tumor samples were obtained using open frozen biopsy, after several unsuccessful attempts. The tumor was composed of sheets of undifferentiated disclosive cells with vesicular nuclei and prominent nucleoli. The differential diagnosis included high-grade lymphoma, germ cell tumor, NUT carcinoma, undifferentiated carcinoma, and sarcoma. The tumor cells were large, arranged in sheets, and did not exhibit glandular or squamous differentiation. Frequent foci of necrosis were noted. There was no evidence of epithelial differentiation on immunohistochemical staining. The SMARCA4 stain showed complete loss of expression of SMARCA4, which is diagnostic. CONCLUSION: In the present case, thoracic SMARCA4-DUT was diagnosed based on clinical features, absence of epithelial differentiation, and negative SMARCA4 expression.

[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.

[Thoracic SMARCA4-deficient undifferentiated tumor resembling malignant lymphoma].

We present a case of thoracic SMARCA4-deficient undifferentiated tumor that needed to be differentiated from malignant lymphoma owing to multiple lymph node swelling and marrow involvement. A 52-year-old man developed multiple lymphadenopathies along with anorexia, general fatigue, fever, and sweating 2 months prior to admission. 18F-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) scan revealed a mass lesion on the right upper lung, generalized lymph node swelling, and bone metastasis, indicating the presence of suspicious lung cancer; therefore, he was referred to our hospital. Malignant lymphoma was suspected at the time of admission because of elevated levels of lactate dehydrogenase (11,977 U/l) and soluble interleukin 2 receptor (2,152 U/ml) as well as marrow infiltration of large abnormal cells. On day 11, the patient died from rapid respiratory failure. Histological and immunohistochemical features of the pleural effusion cell block led to the diagnosis of thoracic SMARCA4-deficient undifferentiated tumor. Thoracic SMARCA4-deficient undifferentiated tumor was recently introduced in the 2021 World Health Organization classification of lung tumors, with most patients being young adults with a history of heavy smoking and poor prognosis. Because of the multiple lymph node swelling and marrow involvement, this undifferentiated tumor should be distinguished from malignant lymphoma.

Promising efficacy of immune checkpoint inhibitor plus chemotherapy for thoracic SMARCA4-deficient undifferentiated tumor.

PURPOSE: Thoracic SMARCA4-deficient undifferentiated tumor (SD-UT) is a highly aggressive disease that is nosologically related to but distinct from SMARCA4-deficient non-small cell lung cancer (SD-NSCLC). No standard treatment guidelines were established for SD-UT. This research explored the efficacy of different treatments in SD-UT, and the prognostic, clinicopathologic and genomic difference between SD-UT and SD-NSCLC. MATERIALS AND METHODS: Information of 25 SD-UT and 22 SD-NSCLC patients diagnosed and treated in Fudan University Shanghai Cancer Center from January, 2017 to September, 2022 was analyzed. RESULTS: SD-UT was similar to SD-NSCLC in characteristics of onset age, male prevalence, heavy smoking history and metastatic pattern. SD-UT showed a rapid relapse pattern after radical therapy. For Stage IV SD-UT patients, immune checkpoint inhibitor (ICI) plus chemotherapy significantly improved median progression-free survival (PFS) compared to traditional chemotherapy as first-line treatment (26.8 vs. 2.73 months, p = 0.0437), while objective response rates of two arms were comparable (71.4% vs. 66.7%). No significant survival differences were observed between SD-UT and SD-NSCLC under similar treatment settings. SD-UT or SD-NSCLC patients receiving ICI in the first line had significantly prolonged OS than those with ICI in the latter lines or without ICI treatment throughout clinical courses. Genetic study found frequent SMARCA4, TP53 and LRP1B mutations in SD-UT. CONCLUSION: To the best of our knowledge, this is the largest series to date to compare the efficacy of ICI-based treatment to chemotherapy and document frequent mutations of LRP1B in SD-UT. ICI plus chemotherapy is an effective strategy for Stage IV SD-UT.

Thoracic SMARCA4-Deficient Undifferentiated Tumor With ALK Fusion Treated With Alectinib Achieved Remarkable Tumor Regression: Case Report.

Recently, SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) has emerged as a distinct subset of lung cancer. Previous studies have suggested that SMARCA4-UT is often associated with smoking-related mutations, such as KRAS and STK11, rather than EGFR or ALK alterations. Nevertheless, no specific precision therapy has been identified for SMARCA4-UT. Here, we report the first case of concomitant ALK rearrangement and SMARCA4 (BRG1) deficiency in a nonsmoking female with thoracic cancer. Alectinib was given as the first-line therapy, and the patient achieved a remarkable complete response. Our case highlights the significance of ALK rearrangement identification for the precise therapeutic potential of SMARCA4-UT.

Usefulness of cell block examination for the cytological diagnosis of thoracic SMARCA4-deficient undifferentiated tumor: A case report.

SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) is a high-grade malignant neoplasm showing undifferentiated or rhabdoid morphology that significantly involves the thorax of adults. It has been reported as SMARCA4-deficient thoracic sarcoma or SMARCA4-deficient non-small cell lung carcinoma according to the findings of immunohistochemical and genetic studies. We report a case of thoracic SMARCA4-UT for which cell block analysis and immunohistochemical staining were useful for the final diagnosis. A 51-year-old man had a chief complaint of left back pain and visited our hospital for further examination. Cytological examination of a left pleural effusion was performed and we also made a cell block of the pleural effusion. Cytological examination revealed polyhedral to round tumor cells. The tumor cells appeared singly or formed loosely cohesive clusters. The nuclei were round to oval, enlarged, and sometimes eccentric with prominent nucleoli with irregular borders. The nuclear chromatin was unevenly distributed. The cytoplasm was vacuolar to eosinophilic. There were no characteristic structures of tumor cells. The cell block revealed many single or loosely cohesive round to epithelioid cells. Some tumor cells often exhibited eccentrically located nuclei and lightly eosinophilic cytoplasm, showing a rhabdoid morphology. On immunohistochemistry, the tumor cells were positive for SOX-2 and they demonstrated significantly reduced SMARCA4 (BRG1) expression; SMARCA2 (BRM) and SMARCB1 (INI1) expression were retained. Accordingly, we made a diagnosis of SMARCA4-UT. This case demonstrates the importance of performing histological and immunohistochemical analysis using cell blocks for immediate diagnosis.

SMARCA4-deficient Undifferentiated Uterine Sarcoma: Clinicopathological Features of an Emerging Entity.

SMARCA4-deficient undifferentiated uterine sarcoma is a recently described molecularly defined entity among the subset of aggressive undifferentiated uterine tumors. Mutation in the SMARCA4 gene is a key driver alteration, as also seen in small cell carcinoma of ovary, hypercalcemic type (SCCOHT) and thoracic undifferentiated carcinoma. Limited number of cases of SMARCA4-deficient undifferentiated uterine sarcoma has been reported in literature. We hereby describe a case of this distinct entity in a 52-year-old woman. Histomorphological examination showed sheets of monomorphic epithelioid cells with a variable proportion of cells displaying rhabdoid features, brisk mitotic activity, and lymphovascular invasion. A panel of immunohistochemical markers was required to exclude the differential diagnoses. The tumor was microsatellite stable. Loss of SMARCA4 expression and intact expression of INI1 in tumor cells by immunohistochemistry (IHC) confirmed the diagnosis of SMARCA4- deficient undifferentiated uterine sarcoma. The patient had a rapidly progressive clinical course.

Conversion Surgery for Advanced Thoracic SMARCA4-Deficient Undifferentiated Tumor With Atezolizumab in Combination With Bevacizumab, Paclitaxel, and Carboplatin Treatment: A Case Report.

A SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) is a rapidly progressing subtype of lung cancer with a poor prognosis and causes early postoperative recurrence among operable patients. In this study, we present a case of SMARCA4-UT with vertebral and chest wall invasion that successfully underwent conversion surgery after treatment with atezolizumab in combination with bevacizumab, paclitaxel, and carboplatin. The surgical specimen comprised SMARCA4-deficient and SMARCA2-positive adenocarcinoma, confirming intratumor heterogeneity. Gene panel analysis revealed no substantial differences in mutant gene profiles among tumors and no differences in SMARCA2 mutations. Furthermore, no recurrence occurred for 9 months after surgery. Thus, this case illustrates the possibility of multidisciplinary treatment including neoadjuvant therapy with immunotherapy and conversion surgery for SMARCA4-UT.