SMARCA4-deficient thoracic sarcoma: a distinctive clinicopathological entity with undifferentiated rhabdoid morphology and aggressive behavior

Unravelling switch/sucrose non-fermentable (SWI-SNF) complex-deficient thoracic tumours: a clinicopathological comparative on undifferentiated tumours and non-small cell lung carcinomas with BRG1 and BRM deficiency

AIMS

This study was undertaken to compare and expand the clinicopathological characteristics of SMARCA4-deficient thoracic undifferentiated tumour (SMARCA4-dUT) and switch/sucrose non-fermentable-deficient non-small cell lung carcinomas (SWI/SNF-dNSCLC) and to address cases with intermediate features.

METHODS

The pathology department archive was searched for all primary mediastinal, pleural and lung-based malignancies that showed aberrant expression of two SWI/SNF proteins the Brahma (BRM) aka SMARCA2 and/or (Brahma-related gene 1 (BRG1) aka SMARCA4. Patient demographics, treatment and clinical outcomes were collected from records and telephonic interviews. Differences in histopathological features and immunohistochemical stains were analysed. Cases with characteristics intermediate between both tumour entities were sequenced to advance our understanding of their biology and to assign them a more accurate classification.

RESULTS

We identified 50 tumours with SMARCA4 and/or SMARCA2 deficiencies, including 23 (46%) SMARCA4-dUT, 18 (36%) SMARCA4-dNSCLC and 2 (4%) SMARCA2-dNSCLC. Dyscohesive or undifferentiated cellular morphology versus frank gland formation along with keratin, claudin-4 and expression of >1 stem cell marker helped classify the SWI/SNF deficient tumours as SMARCA4-dUT or SWI/SNF-dNSCLC (p<0.05). Seven (14%) cases with BRG1 deficiency displayed 'intermediate' features of both SMARCA4-dNSCLC and SMARCA4-dUT and had the shortest overall survival. The smoking-related gene signature was observed on sequencing in all four cases examined.

CONCLUSION

Tumours with intermediate features between SMARCA4-dUT and SWI/SNF-dNSCLC exist and portend an equally poor prognoses. Immunostains, including keratin, claudin-4, TTF1, HepPar1, stem cell markers, along with BRG1 and BRM testing, are essential adjuncts to morphology, while molecular studies can offer supplementary evidence in challenging cases.

Concurrent SMARCA4-deficient and poorly differentiated adenocarcinomas in separate lung lobes: a case report and literature review

BACKGROUND

SMARCA4 and SMARCA2, mutually exclusive catalytic ATPase subunits of human mammalian Switch/Sucrose-Nonfermentable chromatin remodeling enzymes, function as tumor suppressor genes. SMARCA4-deficient adenocarcinoma (SMARCA4-dADC) is a relatively rare subtype of TTF1/P40-negative non-small cell lung cancer. The concurrent presentation of SMARCA4-dADC and poorly differentiated adenocarcinoma with SMARCA2 (also known as BRM) loss in separate lobes of the same patient is even less common. This report describes such a case involving the simultaneous occurrence of these two tumor types in distinct locations within the lungs.

CASE PRESENTATION

A 68-year-old male presented with a three-week history of vague pain in the right side of the chest, with no obvious trigger. Imaging revealed solid masses in the upper and lower lobes of the right lung with bilateral enlarged cervical lymph nodes. So, both of these masses underwent wedge resection. Histopathological examination confirmed that the lower lobe tumor was SMARCA4-dADC, while the upper lobe tumor was diagnosed as poorly differentiated adenocarcinoma. Although histologically similar, both exhibiting predominantly solid sheets and complex glandular structures, the two tumors displayed distinct immunohistochemical and molecular profiles. The lower lobe mass showed complete loss of BRG1 protein expression and partial loss of BRM. Immunohistochemical analysis revealed negative expression of TTF1, Napsin A, SALL4, CD34, and SOX2, and positive expression of CK7, pan-Cytokeratin (CK-pan), and HepPar-1. Molecular analysis identified mutations in SMARCA4, KRAS, and STK11. Conversely, the upper lobe mass retained BRG1 expression but showed complete loss of BRM protein expression, and negative expression of SALL4, CD34, and HepPar-1, positive expression of CK7, CK-pan, TTF1, Napsin A, and SOX2. A KRAS mutation was also detected in this tumor.

CONCLUSION

The simultaneous occurrence of SMARCA4-dADC and conventional adenocarcinoma in different locations within the same patient is exceedingly rare. However, the distinct immunophenotypic and molecular characteristics of SMARCA4-dADC differentiate it as a unique entity from conventional adenocarcinoma. We recommend including SMARCA4 in the marker panel used to evaluate TTF1-negative adenocarcinomas of potential or uncertain pulmonary origin. This report underscores the diagnostic challenge of concurrent SMARCA4-dADC and poorly differentiated adenocarcinoma, proposing a standardized immunohistochemical workflow to guide therapeutic decisions.

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.

SMARCA2 protein: Structure, function and perspectives of drug design

SMARCA2 is an ATPase that regulates chromatin structure via ATP pathways, controlling cell division and differentiation. SMARCA2's bromodomain and ATPase domain, crucial for chromatin remodeling and cell regulation, are therapeutic targets in cancer treatment. This review explores the role of SMARCA2 in cancer development by studying its protein structure and physiological functions. It further discusses the roles and distinctions of SMARCA2 and its related family proteins in cancer. Additionally, this article categorizes known SMARCA2 inhibitors into four classes based on their basic structure and examines their structure-activity relationships (SAR). This review outlines the structural mechanisms of SMARCA2 inhibitors, highlighting interactions with specific amino acids. By analyzing the SAR of inhibitors, we propose a tailored inhibitor model for the bromodomain of SMARCA2, emphasizing α, γ-H-bond donors/acceptors, and β-rigid structures as crucial for effective binding. This research provides guidance for the design and optimization of future drugs targeting the SMARCA2 protein.

Switch/Sucrose Nonfermentable-Deficient Tumors-Morphology, Immunophenotype, Genetics, Epigenetics, Nosology, and Therapy

About 20% of human cancers harbor mutations of genes encoding switch/sucrose nonfermentable (SWI/SNF) complex subunits. Deficiency of subunits of the complex is present in 10% of non-small-cell lung cancers (NSCLC; SMARCA4/SMARCA2 deficient), 100% thoracic SMARCA4/A2-deficient undifferentiated tumors (TSADUDT; SMARCA4/A2 deficient), malignant rhabdoid tumor, and atypical/teratoid tumor (SMARCB1-deficient), >90% of small cell carcinoma of the ovary, hypercalcemic type (SMARCA4/SMARCA2 deficient), frequently in undifferentiated/dedifferentiated endometrial carcinoma (SMARCA4, SMARCA2, SMARCB1, and ARID1A/B deficient), 100% SMARCA4 deficient undifferentiated uterine sarcoma (SMARCA4 deficient); and in various other tumors from multifarious anatomical sites. Silencing of SWI/SNF gene expression may be genomically or epigenetically driven, causing loss of tumor suppression function or facilitating other oncogenic events. The SWI/SNF-deficient tumors share the phenotype of poor or no differentiation, often with a variable component of rhabdoid tumor cells. They present at advanced stages with poor prognosis. Rhabdoid tumor cell phenotype is a useful feature to prompt investigation for this group of tumors. In the thoracic space, the overlap in morphology, immunophenotype, genetics, and epigenetics of SMARCA4/A2-deficient NSCLC and TSADUDT appears more significant. This raises a possible nosologic relationship between TSADUDT and SMARCA4/A2-deficient NSCLC. Increased understanding of the genetics, epigenetics, and mechanisms of oncogenesis in these poor prognostic tumors, which are often resistant to conventional treatment, opens a new horizon of therapy for the tumors.

SMARCA4 Deficiency in Lung Cancer: From Signaling Pathway to Potential Therapeutic Targets

SMARCA4-deficient lung cancer, including thoracic SMARCA4-deficient undifferentiated tumors and SMARCA4-deficient nonsmall-cell lung carcinomas, is a rare and aggressive disease characterized by rapid progression and poor prognosis. This cancer was identified as a distinct entity with specific morphologic and molecular features in the 2021 WHO Classification of Thoracic Tumors. Molecular alterations in SMARCA4 are specific to this type of lung cancer. Deficiency in SMARCA4 suppresses the SWI/SNF tumor suppressor complex, driving tumor progression. Due to the lack of standardized treatment, most patients succumb to the disease within 6 months. This study provides a detailed analysis of the SMARCA4 pathway and its role in lung cancer. We analyzed potential therapeutic targets and agents to offer insights for the precise and effective treatment of SMARCA4-deficient lung cancer.

Brief Report: Clinical Characteristics and Outcomes of Patients With Thoracic SMARCA4-Deficient Undifferentiated Tumors

Introduction

Thoracic SMARCA4-deficient undifferentiated tumors (SMARCA4-UTs) are a recently defined group of aggressive cancers in which the effectiveness of standard treatments for lung cancer is unknown.

Methods

We collected clinical, pathologic, and demographic variables from five institutions for patients whose tumors met criteria for SMARCA4-UTs (undifferentiated phenotype and loss of SMARCA4 (BRG1) by immunohistochemistry).

Results

We identified 92 patients with SMARCA4-UTs; 58 (63%) had stage IV disease at diagnosis and 16 (17%) developed recurrent or metastatic disease after initial diagnosis. Median overall survival from metastatic diagnosis was 7.3 (95% confidence interval [CI]: 4.6-12.8) months. Of patients with metastatic disease, 58 (78%) received first-line systemic treatment. Most often, patients received chemo and immunotherapy combination (41%), chemotherapy alone (33%), or immunotherapy alone (16%). Median progression-free survival from start of systemic therapy was 1.9 (95% CI: 1.4-14.5) months for chemo and immunotherapy, 1.6 (95% CI: 1.1-5.8) months for chemotherapy, and 3.3 (95% CI: 1.2-undefined) months for immunotherapy alone. Five patients had durable responses (≥2 y); all received immunotherapy as part of first-line regimens. Nine (16%) of 55 tumor samples tested had programmed death-ligand 1 expression more than or equal to 50%, with 24 (44%) negative samples. Tumor mutational burden was available in 48 cases (52%), and median was 10.5 (range: 2-48) mutations per megabase.

Conclusions

This multi-institution retrospective cohort analysis revealed a population of patients with short progression-free survival to standard therapies and poor overall survival. A few patients had remarkable response to regimens including immunotherapy. Prospective clinical studies are urgently needed to identify better therapeutic approaches to treat this aggressive malignancy, and this analysis may serve as a benchmark for future clinical trial design.

Case report: Aggressive NSCLC with partial BRG-1 deficiency and KRAS G12C mutation: a case study and treatment challenges

Background

SMARCA4-deficient (BRG-1 deficient) primary thoracic tumors are rare aggressive malignancies associated with poor prognosis. While complete BRG-1 loss is well-documented, the clinical implications of partial BRG-1 deficiency remain unclear. This case report explores a case of mixed lung cancer with partial BRG-1 deficiency and KRAS G12C mutation, highlighting its clinical relevance, treatment challenges, and the importance of comprehensive molecular profiling.

Methods

We performed immunohistochemistry, next-generation sequencing, and PD-L1 expression analysis to characterize the tumor. Treatment included surgical resection, chemotherapy, and immunotherapy.

Case presentation

We present a case of early-stage mixed lung cancer with partial BRG-1 deficiency in a 66-year-old male, treated with surgical resection, chemotherapy, and later, a PD-1 inhibitor. Despite aggressive treatment, rapid progression to brain metastasis was observed, underscoring the need for tailored approaches.

Conclusion

Partial BRG-1 deficiency may lead to aggressive clinical behavior, similar to complete BRG-1 loss. This case emphasizes the importance of comprehensive molecular profiling to guide treatment decisions and suggests further investigation into combined therapeutic strategies, including immunotherapy.

Long-term follow-up of combination therapy with pembrolizumab and anlotinib in thoracic SMARCA4-deficient undifferentiated tumor: a case report and molecular features

Thoracic SMARCA4-deficient undifferentiated tumors (SMARCA4-UTs), recently recognized as a rare malignancy described in the 5th edition of the World Health Organization Classification of Tumors, are characterized by an inactivating mutation in SMARCA4, most commonly found in the mediastinum of male smokers. Despite the aggressive nature and poor prognosis associated with these tumors, which have a median survival time of approximately 4-7 months, no standardized treatment guidelines are currently established. There are currently no reported cases of extended progression-free survival (PFS) in SMARCA4-UT patients treated with surgery and immunotherapy. Here, we report the clinical features and genomic information of a SMARCA4-UT case in which the patient responded significantly to a combination therapy involving surgery, immunotherapy, and amlotinib. A 56-year-old male non-smoker presented with a mass in the superior lobe of left lung and left hilar adenopathy. A left upper lobectomy and lymphadenectomy were performed, and postoperative pathology confirmed that the tumor was Thoracic SMARCA4-UT. The patient subsequently received chemotherapy with pemetrexed and carboplatin. Five months post-operation, the disease progressed with left adrenal metastasis and mediastinal adenopathy. An adrenalectomy was performed, followed by whole exon sequencing (WES). SMARCA4, SMARCA2 and SMARCA1 gene mutations were detected in this case. Given a tumor proportion score (TPS) of 60% for programmed death-ligand 1(22C3)immunoexpression and high TMB(361.32 muts/Mb), a combination of Pembrolizumab plus anlotinib was initiated as a second-line approach. After 46 cycles, the patient demonstrated no disease progression with a PR lasting 31 months and long progression-free survival(PFS) of 43 months. The lung tumor was initially detected in September 2020, and the patient remained alive at the latest follow-up in November 2024. This case offers a long-term follow-up of the effectiveness and safety of combining pembrolizumab and anlotinib in advanced SMARCA4-UT, and substantiates the role of long-term immunotherapy in preventing radiographic/clinical recurrence following surgery. This case illustrates new potential efficacy of immunotherapy in combination with surgery as a treatment approach of SMARCA4-UT.

Rapid Response to Penpulimab Combined With Anlotinib and Chemotherapy in a Thoracic SMARCA4-UT Without PD-L1 Expression: A Case Report and Review of Literature

SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) in the chest is a high-grade malignant tumor that grows rapidly and often carries a poor prognosis. Unfortunately, there are currently no effective treatment available until now. Here, we report a case of SMARCA4-UT in a patient who showed a swift response to a combination treatment of penpulimab, anlotinib, and chemotherapy. A 55-year-old man was diagnosed with thoracic SMARCA4-UT along with metastases to multiple lymph nodes, the pleura, and bones. Immunohistochemical (IHC) testing indicated the absence of PD-L1 expression in tumor cells. He was given sintilimab and anlotinib as first line treatment. However, a follow-up chest CT revealed progressive disease (PD) after the first cycle treatment. Subsequently, the second line regimen was modified to etoposide and cisplatin (EP) combined with anlotinib and penpulimab. The effectiveness evaluation revealed partial remission (PR) following two cycles of the second-line regimen treatment. Notably, the patient's progress-free survival (PFS) exceeds 7 months and the overall survival up to 12 months. Our case implies that a combination of chemotherapy, anlotinib, and penpulimab might offer a promising therapeutic approach for PD-L1-negative thoracic SMARCA4-UT.

Thoracic SMARCA4-Deficient Undifferentiated Tumor in a 40-Year-Old Male Welder With No Smoking History

Thoracic SMARCA4-deficient undifferentiated tumor (TSDUT) is a rare and quite new classification of primary pulmonary malignancy. It is classified as a non-small cell lung cancer, typically associated with smoking, and is highly aggressive. Its clinical features, immunohistochemistry, and pathology are quite unique. In this case report, we describe the clinical course of TSDUT pancoast tumor in a 40-year-old male, without a substantial smoking history, but a significant history of occupational welding.

SMARCA4 and SMARCA2 co-deficiency: An uncommon molecular signature defining a subset of rare, aggressive and undifferentiated malignancies associated with defective chromatin remodeling

Genetic mutations and epigenetic modifications affecting multiple cancer-related genes occur synergistically to drive tumorigenesis. Across a wide spectrum of cancers, pathogenic changes have been identified in members of the SWItch/Sucrose Non-Fermentable complex including its two catalytic subunits, SMARCA4 and SMARCA2. During cancer development, it is not uncommon to lose the function of either SMARCA4 or SMARCA2, however, loss of both together has been reported to be synthetic lethal and therefore unexpected. Co-deficiency of SMARCA4 and SMARCA2 occurs as a pathognomonic feature of the early-onset ovarian cancer Small-cell carcinoma of the ovary, hypercalcemic type. The loss of both catalytic subunits is also described in other rare undifferentiated neoplasms including Thoracic SMARCA4-deficient undifferentiated tumors, Malignant rhabdoid tumors and dedifferentiated or undifferentiated carcinomas, predominantly of lung, gastrointestinal, and endometrial origin. This review provides the first extensive characterization of cancers with concurrent SMARCA4 and SMARCA2 loss through the discussion of shared clinical and molecular features. Further, we discuss the mechanisms triggering the loss of catalytic activity, the cellular processes that are dysfunctional as a consequence, and finally, current therapeutic candidates which may selectively target these cancers.

A case report of SMARCA4-deficient gastric cancer and review of the literature

We report the case of a 50-year-old female with gastric carcinoma. The tumor was positive for epithelial and other immunological markers; however, SMARCA4 was completely inactivated. The histological and immunophenotypic findings were consistent with a diagnosis of SMARCA4-DTS. Next-generation sequencing identified a frameshift mutation in SMARCA4. The pathological diagnosis was SMARCA4-deficient gastric carcinoma. The tumor exhibits a poor response to conventional chemotherapy and has a poor prognosis; therefore, correct diagnosis is necessary. Moreover, new therapies such as EZH2 inhibitors and etoposide should be considered in cases where conventional chemotherapy is ineffective.

Surgical resection following chemoradiotherapy for thoracic SMARCA4-deficient undifferentiated tumor: a report of two cases

BACKGROUND

Thoracic SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) is a high-grade malignant neoplasm with a poor prognosis. Most cases of SMARCA4-UT have extensive chest wall and mediastinum involvement. The efficacy of surgical resection has not been clearly established. Here, we report two surgical cases of SMARCA4-UT with chest wall invasion after chemoradiotherapy.

CASE PRESENTATION

The first patient was a 40-year-old man with back pain. Computed tomography revealed a 6.8 cm mass in contact with the thoracic vertebrae near the intervertebral foramen, which was suspected to involve the third to fifth ribs. The patient was diagnosed with SMARCA4-UT with clinical T3N0M0 stage IIB. The tumor shrank after chemoradiotherapy, and conversion surgery combined with partial vertebrectomy was performed. Histopathological findings revealed 30% residual tumor in the tumor bed. Thirty-six days after surgery, the patient developed multiple liver metastases and peritoneal dissemination. Chemotherapy combined with immune checkpoint inhibitor treatment was performed, resulting in tumor shrinkage. However, peritoneal dissemination recurred within a short interval. The patient died 5 months postoperatively. The second patient was a 74-year-old man with chest pain. Computed tomography revealed a 7.4-cm mass in the left upper lobe with invasion of the third and fourth ribs. The patient was initially diagnosed with non-small cell lung cancer with clinical T4N1M0 stage IIIA. The tumor shrank after induction chemoradiotherapy, and a left upper lobectomy combined with the chest wall resection was performed. Based on histopathological findings, the patient was diagnosed with SMARCA4-UT. The residual tumor percentage was 3%. The patient was followed up for 12 months postoperatively without recurrence.

CONCLUSIONS

We performed the complete resection of SMARCA4-UT following chemoradiotherapy. The two surgical cases had different postoperative courses. Radical surgery after chemoradiotherapy is effective for local control. However, its long-term prognostic efficacy remains unclear. Multidisciplinary approaches and further investigations of novel therapeutic options are required.

Case report: Extraskeletal Ewing sarcoma with a germline pathogenic variant of SMARCA4

SMARCA4 (BRG1) is a core unit of the SWI/SNF complex, regulating gene transcription through chromatin remodeling. Germline SMARCA4 variants have been reported to be associated with various malignancies. Here, we report the first case of extraskeletal Ewing sarcoma in a young female patient with a germline pathogenic variant of SMARCA4 (c.3546 + 1G>A), diagnosed with next generation sequencing (NGS). This alteration was also identified in her familial lineage, including her sister who was previously diagnosed with small cell carcinoma of the ovary, hypercalcemic type, a malignancy highly associated with SMARCA4 mutations. Despite undergoing radical surgery and receiving systemic treatments including VeIP (vinblastine, ifosfamide, cisplatin), and VDC (vincristine, doxorubicin, cyclophosphamide) regimens, the patient succumbed to death due to disease progression. With the implementation of NGS, we anticipate that more cases with SMARCA4 mutations will be diagnosed in the future. Further research is necessary to unveil therapeutic targets associated for this oncogenic alteration.

Thoracic SMARCA4-Deficient Undifferentiated Tumor Mimicking Malignant Pleural Mesothelioma on FDG PET/CT

ABSTRACT

We describe contrast-enhanced CT and FDG PET/CT findings in a case of thoracic SMARCA4-deficient undifferentiated tumor with extensive pleural involvement and mediastinal lymph node metastases. Contrast-enhanced CT showed multiple enhancing right-sided pleural masses and soft tissue plaques and enlarged mediastinal lymph nodes. The pleural lesions and mediastinal lymph nodes showed intense FDG uptake mimicking malignant pleural mesothelioma with mediastinal lymph node metastases.

Small Intestine Metastasis Leads to the Diagnosis of Thoracic SMARCA4-Deficient Undifferentiated Tumor: A Case Report

SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) is a rare and aggressive malignancy characterized by the loss of SMARCA4 protein expression. It typically affects middle-aged male smokers and has a poor prognosis due to its rapid progression and metastatic potential. This case report presents a 73-year-old male diagnosed with a thoracic SMARCA4-UT. Initially diagnosed with stage IVA non-small cell lung cancer, the patient underwent brain tumor resection, radiation, and chemo-immunotherapy. Treatment was halted due to immune-related adverse events. During treatment, a progressing small intestine tumor was discovered, resected, and identified as SMARCA4-UT metastasis through immunohistochemistry, leading to a revised diagnosis of SMARCA4-UT with brain and small intestine metastases. The patient received multimodal treatment, including surgery, radiation, and chemo-immunotherapy. The small intestine metastasis showed resistance to systemic therapy, necessitating surgical intervention. This case highlights the diagnostic challenges and treatment complexities of SMARCA4-UT, emphasizing the importance of comprehensive diagnostic workup and personalized treatment strategies. It demonstrates the potential efficacy of combining systemic therapy with targeted interventions for oligoprogressive disease. The patient's progression-free survival at approximately two years post-diagnosis underscores the need for further research into optimal management strategies for this rare tumor.

Molecularly Defined Thoracic Neoplasms

Molecularly defined neoplasms are increasingly recognized, given the broader application and performance of molecular studies. These studies allow us to better characterize these neoplasms and learn about their pathogenesis. In the thorax, molecularly defined neoplasms include tumors such as NUT carcinoma, SMARCA4-deficient undifferentiated tumor (DUT), primary pulmonary myxoid sarcoma with EWSR1::CREB1 fusion, hyalinizing clear cell carcinoma, and SMARCB1-deficient neoplasms. Overall, these tumors are rare but are now more often recognized given more widely available immunostains such as NUT (NUT carcinoma), BRG1 (SMARCA4-DUT), and INI-1 (SMARCB1-deficient neoplasm). Furthermore, cytogenetic studies for EWSR1 to support a hyalinizing clear cell carcinoma or primary pulmonary myxoid sarcoma are, in general, easily accessible. This enables pathologists to recognize and diagnose these tumors. The diagnosis of these tumors is important for clinical management and treatment. For instance, clinical trials are available for patients with NUT carcinoma, SMARCA4-DUT, and SMACRB1-deficient neoplasms. Herein, our current knowledge of clinical, morphologic, immunophenotypic, and molecular features of NUT carcinomas, SMARCA4-DUT, primary pulmonary myxoid sarcomas, hyalinizing clear cell carcinoma, and SMARCB1-deficient neoplasms will be reviewed.

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.

A Subset of Thoracic SMARCA4-Deficient Undifferentiated Tumors Express GATA3

Thoracic SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) is a rare and highly aggressive malignant neoplasm characterized by high-grade undifferentiated morphologic features and recurrent inactivating mutations of SMARCA4. These tumors consistently exhibit loss of SMARCA4 (BRG1) while displaying variable expression of other nonspecific markers. Recently, we encountered a SMARCA4-UT demonstrating immunoreactivity for GATA3, and we sought to characterize this phenomenon in a larger series.

A total of nine SMARCA4-UTs were examined from 3 large academic institutions. The clinicopathologic and molecular characteristics were studied and GATA3 immunohistochemistry was performed.

The cohort included 5 male and 4 female patients, with a median age of 54 years and a median smoking history of 37 pack-years. At initial diagnosis, mediastinal lymph node involvement was observed in 5 patients (56%) while distant metastases were present in 7 patients (78%). The median survival was 6 months. Histologically, the tumors were characterized by sheets of undifferentiated epithelioid and/or rhabdoid cells, accompanied by frequent mitotic figures and necrosis. Immunohistochemically, all tumors displayed a complete loss of BRG1 expression. Notably, 4 of 9 tumors (44%) were positive for GATA3 expression, including one tumor that exhibited strong and diffuse immunoreactivity.

GATA3 expression in SMARCA4-UT may pose diagnostic challenges, requiring differentiation from other GATA3-positive tumors. This distinction is crucial for accurate prognostication and treatment decisions.

SMARCA4 deficiency and mutations are frequent in large cell lung carcinoma and are prognostically significant

SMARCA4 mutation has emerged as a marker of poor prognosis in lung cancer and has potential predictive value in cancer treatment, but recommendations for which patients require its investigation are lacking. We comprehensively studied SMARCA4 alterations and the clinicopathological significance in a large cohort of immunohistochemically-subtyped non-small cell lung cancer (NSCLC). A total of 1416 patients was studied for the presence of SMARCA4 deficiency by immunohistochemistry (IHC). Thereafter, comprehensive sequencing of tumours was performed for 397 of these patients to study the mutational spectrum of SWI/SNF and SMARCA4 aberrations. IHC evidence of SMARCA4 deficiency was found in 2.9% of NSCLC. Of the sequenced tumours, 38.3% showed aberration in SWI/SNF complex, and 9.3% had SMARCA4 mutations. Strikingly, SMARCA4 aberrations were much more prevalent in large cell carcinoma (LCC) than other histological tumour subtypes. SMARCA4-deficient and SMARCA4-mutated tumours accounted for 40.5% and 51.4% of all LCC, respectively. Multivariable analyses confirmed SMARCA4 mutation was an independent prognostic factor in lung cancer. The immunophenotype of a subset of these tumours frequently showed TTF1 negativity and HepPAR1 positivity. SMARCA4 mutation or its deficiency was associated with positive smoking history and poor prognosis. It also demonstrated mutual exclusion with EGFR mutation. Taken together, the high incidence of SMARCA4 aberrations in LCC may indicate its diagnostic and prognostic value. Our study established the necessity of SMARCA4 IHC in the identification of SMARCA4-aberrant tumours, and this may be of particular importance in LCC and tumours without known driver events.

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.

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.

The golden key to open mystery boxes of SMARCA4-deficient undifferentiated thoracic tumor: focusing immunotherapy, tumor microenvironment and epigenetic regulation

SMARCA4-deficient undifferentiated thoracic tumor is extremely invasive. This tumor with poor prognosis is easily confused with SMARCA4-deficent non-small cell lung cancer or sarcoma. Standard and efficient treatment has not been established. In this review, we summarized the etiology, pathogenesis and diagnosis, reviewed current and proposed innovative strategies for treatment and improving prognosis. Immunotherapy, targeting tumor microenvironment and epigenetic regulator have improved the prognosis of cancer patients. We summarized clinicopathological features and immunotherapy strategies and analyzed the progression-free survival (PFS) and overall survival (OS) of patients with SMARCA4-UT who received immune checkpoint inhibitors (ICIs). In addition, we proposed the feasibility of epigenetic regulation in the treatment of SMARCA4-UT. To our knowledge, this is the first review that aims to explore innovative strategies for targeting tumor microenvironment and epigenetic regulation and identify potential benefit population for immunotherapy to improve the prognosis.

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.

PD-1 antibody in combination with chemotherapy for the treatment of SMARCA4-deficient advanced undifferentiated carcinoma of the duodenum: Two case reports

BACKGROUND

SMARCA4 is a component of chromatin remodeling of SWItch/sucrose-nonfermenting (SWI/SNF) complexes and plays an essential role in oncogenesis. SMARCA4-deficient malignancies arising from the gastrointestinal tract are rare and have a poor prognosis. There is no standard treatment for advanced and undifferentiated SMARCA4-deficient duodenal malignancies. Programmed death 1 (PD-1) antibodies, known as immune checkpoint inhibitor antibodies, potentially play a role in treating gastrointestinal tract malignancies.

CASE SUMMARY

We present two patients with SMARCA4 deficiency and TP53 gene mutation in advanced undifferentiated carcinomas of the duodenum. For both patients, SMARCA4 deficiency was confirmed by immunohistochemical staining for the BRG1 protein, while TP53 gene mutations were observed via next-generation sequencing. Both patients were administered chemotherapy in combination with an anti-PD-1 antibody. The two patients exhibited completely different responses to treatment and had different prognoses. Case 1 experienced rapid progression after PD-1 infusion and chemotherapy, case 2 experienced a remarkable response after treatment, and the progression-free survival was more than 6 months.

CONCLUSION

This study described our clinical and pathological observations of SMARCA4-deficient advanced undifferentiated carcinoma of the duodenum. PD-1 combined with chemotherapy showed a certain efficacy in select patients, providing options for treating these highly malignant tumors. Patients with liver metastases had a worse prognosis than did those with only lymph node metastasis.

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.

Primary Oropharyngeal SMARCA4-Deficient Carcinoma: Expanding the Diagnostic Spectrum in Head and Neck Cancer

With the advent of molecular immunohistochemistry and next generation sequencing, Switch/sucrose non-fermentable (SWI/SNF) chromatin remodeling complex altered tumors have gained recognition recently. SWI/SNF related, matrix associated, actin dependent regulator of chromatin subfamily B member 1 (SMARCB1) and SMARCA4 are the primary SWI/SNF components altered in several recently described undifferentiated malignancies in head and neck region with predilection for paranasal sinuses in SMARCB1-deficient tumors and nasal cavity in SMARCA4-deficient tumors. However, to the best of our knowledge, SMARCA4-deficient tumors of the oropharynx have not been described. We present an unusual case of SMARCA4-deficient carcinoma of the oropharynx (palatine tonsil) which is the first case in the literature, expanding the topographic distribution of SMARCA4-deficient tumors in the head and neck region and emphasizing the importance of BRG1 as an essential immunohistochemical marker for the diagnosis of this distinct entity.

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.

Utility of Immunohistochemistry in the Diagnosis of Pleuropulmonary and Mediastinal Cancers: A Review and Update

CONTEXT.—

Immunohistochemistry has become a valuable ancillary tool for the accurate classification of pleuropulmonary and mediastinal neoplasms necessary for therapeutic decisions and predicting prognostic outcome. Diagnostic accuracy has significantly improved because of the continuous discoveries of tumor-associated biomarkers and the development of effective immunohistochemical panels.

OBJECTIVE.—

To increase the accuracy of diagnosis and classify pleuropulmonary neoplasms through immunohistochemistry.

DATA SOURCES.—

Literature review and the author's research data and personal practice experience.

CONCLUSIONS.—

This review article highlights that appropriately selecting immunohistochemical panels enables pathologists to effectively diagnose most primary pleuropulmonary neoplasms and differentiate primary lung tumors from a variety of metastatic tumors to the lung. Knowing the utilities and pitfalls of each tumor-associated biomarker is essential to avoid potential diagnostic errors.

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.

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.

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.

FDG PET/CT in a Case of Thoracic SMARCA4-Deficient Undifferentiated Tumor

ABSTRACT

Thoracic SMARCA4-deficient undifferentiated tumor is a rare, newly recognized poorly differentiated tumor with poor prognosis. FDG PET/CT findings of thoracic SMARCA4-deficient undifferentiated tumor are rarely reported. We describe FDG PET/CT findings in a case of thoracic SMARCA4-deficient undifferentiated tumor. The tumor presented as a pleural mass, destroyed the adjacent ribs, and showed intense FDG uptake with SUV max of 12.7. This case indicates that thoracic SMARCA4-deficient undifferentiated tumor should be included in the differential diagnosis of FDG-avid pleural lesions.

Superior Identification of Metastatic Lesions by 68 Ga-FAPI-46 to 18 F-FDG PET/CT in a Case of SMARCA4-Deficient Undifferentiated Carcinoma of Stomach

ABSTRACT

SMARCA4-deficient undifferentiated carcinoma is a new clinical entity characterized by SMARCA4 inactivation and has a dismal prognosis because of rapid growth. In this case, we reported 18 F-FDG and 68 Ga-FAPI-46 PET/CT imaging findings in a patient with SMARCA4-deficient undifferentiated carcinoma of stomach. 68 Ga-FAPI-46 PET/CT showed much higher tumor-to-background contrast of primary tumor and revealed more metastatic lesions than 18 F-FDG PET/CT. This case demonstrated the superiority of 68 Ga-FAPI PET/CT over 18 F-FDG for identifying both primary and metastatic lesions in SMARCA4-deficient undifferentiated carcinoma. This observation may add the information on the benefit of FAPI PET in oncology imaging.

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.

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.

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.

Molecular, clinicopathological characteristics and surgical results of resectable SMARCA4-deficient thoracic tumors

PURPOSE

SMARCA4-deficient thoracic tumors are rapid aggressive malignancies, often diagnosed at an advanced and inoperable stage. The value of pulmonary resection for resectable SMARCA4-deficient thoracic tumors is largely unknown.

METHODS

In this observational study, we included 45 patients who received surgery for stage I-III SMARCA4-deficient tumors. We compared the molecular, clinicopathological characteristics and survival between SMARCA4-dNSCLC and SMARCA4-deficient undifferentiated tumor (SMARCA4-dUT) patients.

RESULTS

Thirty-four SMARCA4-dNSCLC and 11 SMARCA4-dUT patients were included in this study. Molecular profiles were available in 33 out of 45 patients. The most common mutated gene was TP53 (21, 64%), and followed by STK11 (9, 27%), KRAS (5, 15%), FGFR1 (4, 12%) and ROS1 (4, 12%). There were 3 patients that harbored ALK mutation including 1 EML4-ALK rearrangement. There were 2 patients that harbored EGFR rare site missense mutation. SMARCA4-dUT patients had significance worse TTP (HR = 4.35 95% CI 1.77-10.71, p = 0.001) and OS (HR = 4.27, 95% CI 1.12-16.35, p = 0.022) compared to SMARCA4-dNSCLC patients. SMARCA4-dUT histologic type, stage II/III, R1/2 resection and lymphovascular invasion were independent poor prognostic predictors for both TTP and OS. There were 8 patients who received immunotherapy, the objective response rate was 50%. The SMARCA4-dNSCLC patient with ALK rearrangement was treated with crizotinib as second-line therapy, and achieved stable disease for 9.7 months.

CONCLUSION

Patients with SMARCA4-deficient tumors have a high probability of early recurrence after surgery, except for stage I patients. Immunotherapy seems to be a valuable strategy to treat recurrence.

A Case Report of SMARCA4-Deficient Thoracic Sarcoma: A Rare and Aggressive Disease With a Grim Prognosis

SMARCA4-deficient thoracic sarcoma (DTS) is a rare malignancy defined by inactivating SMARCA4 mutations leading to protein loss. It was recently described as an aggressive disease with a dismal prognosis, mostly affecting young men with a history of heavy smoking. Histologically, SMARCA4-DTS is a poorly differentiated tumor with rhabdoid or epithelioid features that can be distinguished from other soft tissue, and thoracic sarcomas by a higher tumor mutation burden (TMB) and the presence of smoking signatures, including KRAS, STK11, and KEAP1 mutations. Currently, there is no approved treatment for SMARCA4-DTS, which is known to be chemo-resistant, but more recent studies have shown some effectiveness with immune checkpoint inhibitors. We report the case of a 42-year-old man with a family history of cancer who was admitted to the hospital with acute respiratory distress and superior vena cava syndrome. He had been experiencing thoracic pain, dry cough, dyspnea, fatigue, and unintentional weight loss for a month. Imaging revealed multiple masses and lymph nodes in the chest, as well as pleural effusion. PET scan showed widespread metastases. A cervical lymph node biopsy confirmed the diagnosis of SMARCA4-deficient thoracic sarcoma. Unfortunately, his general condition did not allow an aggressive treatment. He was started on Pazopanib 800mg per day, but deteriorated rapidly and passed away. This report highlights the aggressive nature and unfavorable prognosis associated with SMARCA4-deficient thoracic sarcoma. Accurate diagnosis of this entity can be challenging due to its unique marker expression and unfamiliar histological features. Currently, there are no established treatment strategies for this condition; however, recent studies have shown promising results with immune checkpoint inhibitors and targeted therapies. Further research is necessary to identify the most effective treatment approaches for SMARCA4-DTS.

Characterization of Switch/Sucrose Nonfermenting Complex Proteins and Nestin Expression in a Cohort of Pediatric Central Nervous System Tumors

Tumors of the central nervous system (CNS) in pediatric patients have undergone significant diagnostic refinement through the use of immunohistochemistry (IHC) and molecular techniques. The utility of these novel IHC antibodies has been demonstrated with the inactivation of the switch/sucrose nonfermenting (SWI/SNF) chromatin-remodeling complex in the diagnosis of atypical teratoid/rhabdoid tumors, predominantly through the loss of integrase interactor 1 (INI1; SMARCB1 ). Alternatively, these tumors may have inactivation of brahma-related gene 1 (BRG1; SMARCA4 ) in a subset of cases. The role of other SWI/SNF component proteins and their expression in pediatric brain tumors is not well established. Nestin, an intermediate filament, has been shown to be present in some pediatric CNS tumors, but of uncertain diagnostic and prognostic significance. We sought to explore the immunohistochemical expression profile for common SWI/SNF subunits and nestin in a pediatric CNS tumor cohort. Using a 118-sample tissue microarray, we performed IHC for INI1, BRG1, brahma (BRM), ARID1A, ARID1B, polybromo 1, and nestin. In 19 cases, INI1 was lost and BRG1 was lost in 2 cases. Interestingly, 6 cases originally diagnosed as primitive neuroectodermal tumors showed isolated loss of BRM. Other SWI/SNF proteins did not provide further diagnostic resolution. Nestin was positive in 76.2% of INI1/BRG1-deficient tumors, compared with 29.1% in INI1/BRG1-intact tumors yielding a sensitivity of 76.2%, specificity of 68.0%, and a P value of <0.001, but nestin positivity did not correlate specifically with poor outcomes. In conclusion, we confirm the utility of BRG1 IHC in the workup of pediatric CNS tumors, which may facilitate a difficult diagnosis when conventional markers are inconclusive, or as a first-line marker in cases where intraoperative smears are suggestive of atypical teratoid/rhabdoid tumor. Although nestin expression was associated with SWI/SNF inactivation, it did not yield statistically significant diagnostic or prognostic information in our study. Interestingly, we identified 6 tumors with isolated BRM IHC loss, the significance of which is uncertain but warrants further investigation.

Borderline With Bad Behavior: An Unusual Low-grade Serous Carcinoma With Dedifferentiation From a Serous Borderline Tumor

The pathogenesis of serous ovarian tumors has been extensively investigated, with a dualistic model dividing these cancers into 2 groups. Type I tumors, including low-grade serous carcinoma, is characteristic for concurrent presence of borderline tumors, less atypical cytology, relatively indolent biologic behavior, and molecular aberrations related to the MAPK pathway with chromosomal stability. Meanwhile, type II tumors, such as high-grade serous carcinoma, are notable for no significant association with borderline tumors, higher grade cytology, more aggressive biologic behavior, and TP53 mutations along with chromosomal instability. We describe a case of morphologic low-grade serous carcinoma with focally increased cytologic atypia arising in serous borderline tumors involving both ovaries, which demonstrated highly aggressive behavior despite several years of surgical and chemotherapeutic management. Each recurrent specimen contained more uniform higher grade morphology than what was seen in the original specimen. Immunohistochemical and molecular studies in both the original tumor and the most recent recurrence demonstrate identical mutations in the MAPK genes, but with additional mutations in the latter, notably an acquisition of a variant of possible clinical significance in the SMARCA4 gene, which is associated with dedifferentiation and aggressive biologic behavior. This case challenges our current and still evolving understanding of the pathogenesis, biologic behavior, and expected clinical outcome of low-grade serous ovarian carcinomas. It also underscores the need for further investigation into this complicated tumor.

Thoracic SMARCA4-deficient undifferentiated tumor

Thoracic SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) is a recently described smoking-related malignancy. The pathogenesis of SMARCA4-UT is the mutational inactivation and loss of expression of a subunit encoding the mammalian switch/sucrose nonfermenting ATPase-dependent chromatin remodeling complex (which can be mobilized using adenosine triphosphate hydrolysis nucleosomes and regulate other cellular processes including development, differentiation, proliferation, and apoptosis), in particular SMARCA4 and SMARCA2. The dynamic activity of this complex plays an important role in regulating the activation and repression of gene expression programs. SMARCA4-UT exhibits morphological features similar to the malignant rhabdoid tumor (MRT), small cell carcinoma of the ovary of the hypercalcemic type (SCCOHT), and INI1-deficient tumor, but SMARCA4-UT differs from SCCOHT and MRT from a genomic perspective. SMARCA4-UT mainly involves the mediastinum and lung parenchyma, and appears as a large infiltrative mass that easily compresses surrounding tissues. At present, chemotherapy is a common treatment, but its efficacy is not clear. Moreover, the inhibitor of the enhancer of zeste homolog 2 showed promising efficacy in some patients with SMARCA4-UT. This study aimed to review the clinical characteristics, diagnosis, treatment, and prognosis of SMARCA4-UT.

Malignant undifferentiated epithelioid neoplasms with MAML2 rearrangements: A clinicopathologic study of seven cases demonstrating a heterogenous entity

Among mesenchymal tumors, MAML2 gene rearrangements have been described in a subset of composite hemangioendothelioma and myxoinflammatory fibroblastic sarcoma (MIFS). However, we have recently encountered MAML2-related fusions in a group of seven undifferentiated malignant epithelioid neoplasms that do not fit well to any established pathologic entities. The patients included five males and two female, aged 41-71 years old (median 65 years). The tumors involved the deep soft tissue of extremities (hip, knee, arm, hand), abdominal wall, and the retroperitoneum. Microscopically, the tumors consisted of solid sheets of atypical epithelioid to histiocytoid cells with abundant cytoplasm. Prominent mitotic activity and necrosis were present in 4 cases. In 3 cases, the cells displayed hyperchromatic nuclei or conspicuous macronucleoli, and were admixed with background histiocytoid cells and a lymphoplasmacytic infiltrate. By immunohistochemistry (IHC), the neoplastic cells had a nonspecific phenotype. On targeted RNA sequencing, MAML2 was the 3' partner and fused to YAP1 (4 cases), ARHGAP42 (2 cases), and ENDOD1 (1 case). Two cases with YAP1::MAML2 harbored concurrent RAF kinase fusions (RBMS3::RAF1 and AGK::BRAF, respectively). In 2 cases with targeted DNA sequencing, mutations in TP53, RB1 and PTEN were detected in 1 case, and PDGFRB mutations, CCNE1 amplifications and CDKN2A/2B deletion were detected in another case, which showed strong and diffuse PDGFRB expression by IHC. Of the 4 cases with detailed clinical history (median follow-up period 8 months), three developed distant metastatic disease (one of which died of disease); one case remained free of disease 3 years following surgical excision. In conclusion, we describe a heterogeneous series of MAML2-rearranged undifferentiated malignant epithelioid neoplasms, a subset of which may overlap with a recently described MIFS variant with YAP1::MAML2 fusions, further expanding the clinicopathologic spectrum of mesenchymal neoplasms with recurrent MAML2 gene rearrangements.

SMARCA4 and SMARCE1 in gastric cancer: Correlation with ARID1A, and microsatellite stability, and SMARCE1/ERBB2 co-amplification

BACKGROUND

Recent studies have shown an association between certain subunits of the SWI/SNF complex with specific tumor characteristics in gastric cancer (GC). In an earlier study, we applied multiregional whole exome sequencing on multiple primary tumor samples and found alterations of the SWI/SNF complex in 78% of the cases. ERBB2, which encodes for Her2/neu, is a well-known predictive biomarker used to guide the treatment of GC in the palliative setting. SMARCE1, which encodes for a subunit of the SWI/SNF complex, is localized in close genetic proximity to ERBB2.

AIM

As little is known about the significance of the SWI/SNF complex in GC biology and the potential relationship between ERBB2 and SMARCE1 upregulation, we examined the expression patterns of SMARCA4 and SMARCE1, two mutually exclusive catalytic ATPase subunits of the SWI/SNF complex, in a well characterized GC cohort.

MATERIALS AND METHODS

The expression of SMARCA4 and SMARCE1 was studied by immunohistochemistry in connection with clinicopathological patient characteristics in a cohort of 468 GCs. Digital droplet polymerase chain reaction was performed for amplification analysis on ERBB2 and SMARCE1.

RESULTS

Immunohistochemical staining of whole-mount tissue sections found a diffusely "gray scale" expression of SMARCA4 in 446 (95.2%) GCs and of SMARCE1 in 463 (98.8%) GCs. The expression of SMARCA4 and SMARCE1 correlated significantly with ARID1A, p53, and microsatellite status. No correlation was found with the patient prognosis. The amplification analysis of SMARCE1 showed amplification in 4 of 34 cases. In 3 of 34 cases, SMARCE1 was co-amplified with ERBB2. We also found a co-expression of SMARCE1 and Her2/neu in a subset of patients.

CONCLUSION

While the effect of a co-amplification is currently unknown, synergistic effects of SMARCE1 and Her2/neu overexpression should be explored in future studies, holding potential for an improved treatment of GC.

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.

Awake Uniportal VATS for the Evacuation of an Extensive, Superinfected Hemothorax in a Patient with Advanced Mediastinal SMARCA4-Deficient Tumor

Background  The so-called nonintubated or awake video-assisted thoracoscopic surgery (NIVATS) is performed on spontaneously breathing patients, which was shown to reduce postoperative complications and shorten hospital stay. Case Description  Awake uniportal VATS was indicated for the evacuation of an extensive, superinfected hemothorax with symptomatic mediastinal shift in a patient with advanced mediastinal SMARCA4-deficient tumor and declined condition, who did not allow a general anesthetic procedure and was not a candidate for extensive surgery. Conclusion  This short microinvasive intervention was a prerequisite to stabilize the threat to the patient's life and thus potentially enable any further tumor-specific therapy.

Malignant undifferentiated and rhabdoid tumors of the gastroesophageal junction and esophagus with SMARCA4 loss: a case series

Undifferentiated SMARCA4-deficient carcinoma of the esophagus and gastroesophageal junction is a rare, highly aggressive, and diagnostically challenging malignancy. Here we present a case series of high-grade undifferentiated malignant neoplasms of the esophagus and gastroesophageal junction that share SMARCA4 loss by immunohistochemistry and demonstrate a rhabdoid phenotype. Five cases are presented, including 4 men and 1 woman with an age range of 48-79 years. Interestingly, only one case showed intestinal metaplasia (Barrett's esophagus) and no cases demonstrated glandular dysplasia or glandular differentiation. In all, the lesional cells were immunoreactive with antibodies to keratins (3/5), CD34 (2/4), and CD138 (4/5). SMARCA4 expression was diffusely lost in all cases, whereas SMARCB1 expression was intact. OncoScan™ assay demonstrated loss of SMARCA4 in all cases analyzed. Additional OncoScan™ findings included abnormalities of CDKN2A in 2 of 3 cases, abnormalities of TP53 in 2 of 3 cases, and abnormalities of PTPRD in 2 of 3 cases, among other abnormalities.

Primary cutaneous SMARCA4-deficient undifferentiated malignant neoplasm: first two cases with clinicopathologic and molecular comparison to eight visceral counterparts

SMARCA4-deficient undifferentiated malignant neoplasms (SD-UMN) comprise a group of aggressive tumors with epithelioid morphology that are characterized by loss of function of SMARCA4, a component of the SWI/SNF chromatin remodeling complex. SD-UMN was first recognized in the thoracic cavity but is now appreciated to occur at multiple anatomic sites. A notable exception has been skin. Here we report the first two cases of primary cutaneous SD-UMN and compare their features to a cohort of eight visceral cases arising in lung, gastrointestinal tract, and gallbladder. Evidence for a bona fide cutaneous origin included extensive clinical, radiologic, and serologic analyses that failed to identify a metastatic source as well as the molecular identification of a UV-associated mutational pattern. The cutaneous cases showed strikingly similar morphologic, immunohistochemical, and molecular features to the visceral cases, strongly suggesting that they belong to this family of tumors. In addition to biallelic inactivation of SMARCA4, both cutaneous tumors also showed biallelic inactivation of TP53 and CDKN2A, findings which also appear common in visceral cases. One patient died of disease at 18 months after diagnosis, consistent with the aggressive nature of this tumor. Our results expand the anatomic spectrum of SD-UMN, adding this entity to an already challenging differential diagnosis that includes melanoma, squamous cell carcinoma, Merkel cell carcinoma, epithelioid sarcoma, and others. Given the potentially aggressive nature of SD-UMN, the timely and accurate diagnosis of this entity may have implications for prognosis and therapy.