Pancreatic undifferentiated rhabdoid carcinoma: KRAS alterations and SMARCB1 expression status define two subtypes

Clinicogenomic landscape of pancreatic adenocarcinoma identifies KRAS mutant dosage as prognostic of overall survival

Nearly all pancreatic adenocarcinomas (PDAC) are genomically characterized by KRAS exon 2 mutations. Most patients with PDAC present with advanced disease and are treated with cytotoxic therapy. Genomic biomarkers prognostic of disease outcomes have been challenging to identify. Herein leveraging a cohort of 2,336 patients spanning all disease stages, we characterize the genomic and clinical correlates of outcomes in PDAC. We show that a genomic subtype of KRAS wild-type tumors is associated with early disease onset, distinct somatic and germline features, and significantly better overall survival. Allelic imbalances at the KRAS locus are widespread. KRAS mutant allele dosage gains, observed in one in five (20%) KRAS-mutated diploid tumors, are correlated with advanced disease and demonstrate prognostic potential across disease stages. With the rapidly expanding landscape of KRAS targeting, our findings have potential implications for clinical practice and for understanding de novo and acquired resistance to RAS therapeutics.

Characterization of undifferentiated carcinomas of the pancreas with and without osteoclast-like giant cells

BACKGROUND

Undifferentiated carcinoma (UC) is a rare subtype of pancreatic cancer distinguished from UC with osteoclast-like giant cells (UC-OGC) in 2019, affecting interpretation of literature that does not distinguish these subtypes. We sought to identify translationally relevant differences between these 2 variants and compared with pancreatic ductal adenocarcinoma.

METHODS

We characterized clinical and multiomic differences between UC (n = 32) and UC-OGC (n = 15) using DNA sequencing, RNA sequencing, and multiplex immunofluorescence and compared these findings with pancreatic ductal adenocarcinoma.

RESULTS

Characteristics at diagnosis were similar between UC and UC-OGC, though the latter was more resectable (P = .009). Across all stages, median overall survival was shorter for UC than for UC-OGC (0.4 years vs 10.8 years, respectively; P = .003). This shorter survival was retained after stratification by resection, albeit without statistical significance (1.8 years vs 11.9 years, respectively; P = .08). In a subset of patients with available tissue, the genomic landscape was similar among UC (n = 9), UC-OGC (n = 5), and pancreatic ductal adenocarcinoma (n = 159). Bulk RNA sequencing was deconvoluted and, along with multiplex immunofluorescence in UC (n = 13), UC-OGC (n = 5), and pancreatic ductal adenocarcinoma (n = 16), demonstrated statistically significantly increased antigen-presenting cells, including M2 macrophages and natural killer cells, and decreased cytotoxic and regulatory T cells in UC and UC-OGC vs pancreatic ductal adenocarcinoma. Findings were similar between UC and UC-OGC , except for decreased regulatory T cells in UC-OGC (P = .04).

CONCLUSIONS

In this series, UC was more aggressive than UC-OGC, with these variants having more antigen-presenting cells and fewer regulatory T cells than pancreatic ductal adenocarcinoma, suggesting potential for immune-modulating therapies in the treatment of these pancreatic cancer subtypes.

SMARCB1-deficient malignant neoplasm of the pancreas with heterogeneous morphologies that cannot be classified into existing histologic types

A 50-year-old male with a pancreatic tail tumor underwent distal pancreatectomy. At 14 and 27 months after the primary surgery, metachronous liver metastases were identified and partial hepatectomies were performed for each. Pathologic findings of the primary pancreatic tumor were heterogeneous, but they essentially categorized into two components based on their cytologic features: (i) clear cell component and (ii) epithelioid cell component. The metastatic hepatic tumor was entirely composed of the epithelioid cell component. SMARCB1 expression was lost by immunohistochemistry and heterozygous deletion of SMARCB1 was identified by fluorescence in situ hybridization for both the primary and metastatic tumors. Targeted DNA sequencing of a metastatic hepatic tumor sample was performed and SMARCB1 loss was identified. Based on the morphologic, immunohistochemical, and molecular analyzes, the present case was difficult to classify into any of the existing entities. SMARCB1 deficiency might play a key role in the tumorigenesis.

SWI/SNF Complex-Deficient Undifferentiated Carcinoma of the Pancreas: Clinicopathologic and Genomic Analysis

Inactivating alterations in the SWItch/Sucrose NonFermentable (SWI/SNF) Chromatin Remodeling Complex subunits have been described in multiple tumor types. Recent studies focused on SMARC subunits of this complex to understand their relationship with tumor characteristics and therapeutic opportunities. To date, pancreatic cancer with these alterations has not been well studied, although isolated cases of undifferentiated carcinomas have been reported. Herein, we screened 59 pancreatic undifferentiated carcinomas for alterations in SWI/SNF complex-related (SMARCB1 [BAF47/INI1], SMARCA4 [BRG1], SMARCA2 [BRM]) proteins and/or genes using immunohistochemistry and/or next-generation sequencing. Cases with alterations in SWI/SNF complex-related proteins/genes were compared with cases without alterations, as well as with 96 conventional pancreatic ductal adenocarcinomas (PDAC). In all tumor groups, mismatch repair and PD-L1 protein expression were also evaluated. Thirty of 59 (51%) undifferentiated carcinomas had a loss of SWI/SNF complex-related protein expression or gene alteration. Twenty-seven of 30 (90%) SWI-/SNF-deficient undifferentiated carcinomas had rhabdoid morphology (vs 9/29 [31%] SWI-/SNF-retained undifferentiated carcinomas; P < .001) and all expressed cytokeratin, at least focally. Immunohistochemically, SMARCB1 protein expression was absent in 16/30 (53%) cases, SMARCA2 in 4/30 (13%), and SMARCA4 in 4/30 (13%); both SMARCB1 and SMARCA2 protein expressions were absent in 1/30 (3%). Five of 8 (62.5%) SWI-/SNF-deficient undifferentiated carcinomas that displayed loss of SMARCB1 protein expression by immunohistochemistry were found to have corresponding SMARCB1 deletions by next-generation sequencing. Analysis of canonical driver mutations for PDAC in these cases showed KRAS (2/5) and TP53 (2/5) abnormalities. Median combined positive score for PD-L1 (E1L3N) was significantly higher in the undifferentiated carcinomas with/without SWI/SNF deficiency compared with the conventional PDACs (P < .001). SWI-/SNF-deficient undifferentiated carcinomas were larger (P < .001) and occurred in younger patients (P < .001). Patients with SWI-/SNF-deficient undifferentiated carcinoma had worse overall survival compared with patients with SWI-/SNF-retained undifferentiated carcinoma (P = .004) and PDAC (P < .001). Our findings demonstrate that SWI-/SNF-deficient pancreatic undifferentiated carcinomas are frequently characterized by rhabdoid morphology, exhibit highly aggressive behavior, and have a negative prognostic impact. The ones with SMARCB1 deletions appear to be frequently KRAS wild type. Innovative developmental therapeutic strategies targeting this genomic basis of the SWI/SNF complex and the therapeutic implications of EZH2 inhibition (NCT03213665), SMARCA2 degrader (NCT05639751), or immunotherapy are currently under investigation.

Histological variants of pancreatic ductal adenocarcinoma: a survival analysis

PURPOSE

Pancreatic ductal adenocarcinoma (PDAC) can be classified into distinct histological subtypes based on the WHO nomenclature. The aim of this study was to compare the prognosis of conventional PDAC (cPDAC) against the other histological variants at the population level.

METHODS

The Surveillance, Epidemiology and End Results (SEER) database was used to identify patients with microscopically confirmed PDAC. These patients were divided into 9 histological subgroups. Overall survival was assessed using the Kaplan-Meier method and Cox regression models stratified by tumor histology.

RESULTS

A total of 159,548 patients with PDAC were identified, of whom 95.9% had cPDAC, followed by colloid carcinoma (CC) (2.6%), adenosquamous carcinoma (ASqC) (0.8%), signet ring cell carcinoma (SRCC) (0.5%), undifferentiated carcinoma (UC) (0.1%), undifferentiated carcinoma with osteoclast-like giant cells (UCOGC) (0.1%), hepatoid carcinoma (HC) (0.01%), medullary carcinoma of the pancreas (MCP) (0.006%) and pancreatic undifferentiated carcinoma with rhabdoid phenotype (PUCR) (0.003%). Kaplan-Meier curves showed that PUCR had the worst prognosis (median survival: 2 months; 5-year survival: 0%), while MCP had the best prognosis (median survival: 41 months; 5-year survival: 33.3%). In a multivariable Cox model, several histological subtypes (i.e. CC, ASqC, SRCC, UCOGC) were identified as independent predictors of overall survival when compared to cPDAC.

CONCLUSION

PDAC is a heterogenous disease and accurate identification of variant histology is important for risk stratification, as these variants may have different biological behavior.

Sarcomatoid carcinoma of the pancreas (Review)

Sarcomatoid carcinoma of the pancreas (SCP) is a rare and aggressive subtype of undifferentiated pancreatic ductal adenocarcinoma, with a generally poor prognosis and only sporadic cases reported worldwide. Histologically, the most notable feature of SCP is the presence of abundant of mesenchymatoid spindle tumor cells in the tumor, which lack glandular differentiation. Immunohistochemically, SCP is characterized by the expression of both mesenchymal and epithelial markers. With only a few reported cases, there is limited knowledge about its molecular and clinicopathological characteristics. Therefore, the present study performed a literature search to identify all relevant published studies. The present review provides an overview of the histogenesis, diagnosis, genetic features, prognosis and treatment of SCP, specifically focusing on the molecular alterations. Furthermore, a single-center experience is reported, which adds to the limited evidence available in the literature.

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.

A narrative review on rare types of pancreatic cancer: should they be treated as pancreatic ductal adenocarcinomas?

Pancreatic cancer is one of the deadliest malignancies in humans and it is expected to play a bigger part in cancer burden in the years to come. Pancreatic ductal adenocarcinoma (PDAC) represents 85% of all primary pancreatic malignancies. Recently, much attention has been given to PDAC, with significant advances in the understanding of the mechanisms underpinning disease initiation and progression, along with noticeable improvements in overall survival in both localized and metastatic settings. However, given their rarity, rare histological subtypes of pancreatic cancer have been underappreciated and are frequently treated as PDAC, even though they might present non-overlapping molecular alterations and clinical behavior. While some of these rare histological subtypes are true variants of PDAC that should be treated likewise, others represent separate clinicopathological entities, warranting a different therapeutic approach. In this review, we highlight clinical, pathological, and molecular aspects of rare histological types of pancreatic cancer, along with the currently available data to guide treatment decisions.

SMARCB1/INI1-deficient undifferentiated tumour of the thorax: a case report and review of the literature

The 5th WHO classification of thoracic tumours includes thoracic SMARCA4-deficient undifferentiated tumour (SMARCA4-UT) among the "other epithelial tumours of the lung" chapter. Herein, we present a case of undifferentiated thoracic neoplasm with retention of SMARCA4 expression, lack of NUT fusion protein and loss of SMARCB1/INI1 expression. After presenting the clinical and pathological features of the tumour, we carried out a review of the literature on the same topic. Albeit very rare, we believe this entity should be included in the heterogeneous group of undifferentiated neoplasms of the thorax.

SWI/SNF chromatin remodeling complex in pancreatic ductal adenocarcinoma: Clinicopathologic and immunohistochemical study

The SWItch/Sucrose Non-Fermentable (SWI/SNF) complex is a multimeric protein involved in transcription regulation and DNA damage repair. SWI/SNF complex abnormalities are observed in approximately 14-34 % of pancreatic ductal adenocarcinomas (PDACs). Herein, we evaluated the immunohistochemical expression of a subset of the SWI/SNF complex proteins (ARID1A, SMARCA4/BRG1, SMARCA2/BRM, and SMARCB1/INI1) within our PDAC tissue microarray to determine whether SWI/SNF loss is associated with any clinicopathologic features or patient survival in PDAC. In our cohort, 13 of 353 (3.7 %) PDACs showed deficient SWI/SNF complex expression, which included 11 (3.1 %) with ARID1A loss, 1 (0.3 %) with SMARCA4/BRG1 loss, and 1 (0.3 %) with SMARCA2/BRM loss. All cases were SMARCB1/INI1 proficient. The SWI/SNF-deficient PDACs were more frequently identified in older patients with a mean age of 71.6 years (SD = 7.78) compared to the SWI/SNF-proficient PDACs which occurred at a mean age of 65.2 years (SD = 10.95) (P = 0.013). The SWI/SNF-deficient PDACs were associated with higher histologic grade, compared to the SWI/SNF-proficient PDACs (P = 0.029). No other significant clinicopathologic differences were noted between SWI/SNF-deficient and SWI/SNF-proficient PDACs. On follow-up, no significant differences were seen for overall survival and progression-free survival between SWI/SNF-deficient and SWI/SNF-proficient PDACs (both with P > 0.05). In summary, SWI/SNF-deficient PDACs most frequently demonstrate ARID1A loss. SWI/SNF-deficient PDACs are associated with older age and higher histologic grade. No other significant associations among other clinicopathologic parameters were seen in SWI/SNF-deficient PDACs including survival.

[Histopathologic diagnosis of solid and cystic pancreatic lesions with a focus on ductal adenocarcinoma : A vademecum for daily practice]

Pancreas pathology is constantly evolving and can present various challenges for pathologists. This paper is focused on providing helpful hints for daily routine diagnostics. During histopathological analysis of pancreas biopsies, pancreatic ductal adenocarcinoma must be distinguished not only from other solid neoplasms, but especially from its mimicker, autoimmune pancreatitis. This can be achieved by a systematic workup following clear diagnostic criteria. When analyzing samples from cystic pancreatic lesions, mucin-producing neoplasms must be detected due to their role as pancreatic cancer precursors; molecular analyses can help considerably with their detection and distinction. During frozen section examination, evaluation of the pancreatic neck margin and analysis of unclear lesions of the liver are two important tasks, which are explained further in this article. A special challenge is the evaluation of neoadjuvant treated pancreatic cancer, which requires a detailed macroscopic and microscopic workup. Finally, current advances in precision oncology and emerging approaches for pancreatic cancer within this field are discussed. With the advancement of technical possibilities and their increasingly broad implementation, the classification systems in pancreatic pathology will continue to gain in complexity, but also in accuracy.

SMARCB1/INI1-Deficient Poorly Differentiated Carcinoma of the Colon With Rhabdoid Features-A Rare Tumor With Serrated Phenotype: Case Report and Review of Literature

Poorly differentiated colonic carcinoma with rhabdoid features is a rarely described entity. Our knowledge regarding the molecular phenotype of the tumor is evolving. We herein report a similar tumor with rhabdoid differentiation identified in the splenic flexure, which on histological examination showed a poorly differentiated phenotype with epithelioid to spindled morphology, tumor giant cells, and rhabdoid differentiation. The tumor was mismatch repair-proficient, deficient of INI1/SMARCB1, KRAS mutated (A146×), BRAFV600E mutated (c.1799T > A), and NRAS wild-type, indicating serrated differentiation in the tumor. The patient died after 3.5 months post-surgery. INI1-deficient poorly differentiated carcinoma of the colon is a rare, aggressive colonic malignancy showing a serrated phenotype. Routine identification and subtyping are important keeping in mind the distinct tumor phenotype, resistance to conventional chemotherapy, and dismal prognosis.

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.

A Rare Case of Rhabdoid Pancreatic Carcinoma: Prolonged Disease-Free Survival Following Upfront Resection and Adjuvant Chemotherapy

The rhabdoid subtype of undifferentiated pancreatic carcinoma is rarely reported. The clinical course of this disease is therefore poorly understood, although it is apparently an aggressive malignancy. We herein discuss the case of a 69-year-old man presenting with a rapidly enlarging mass of the pancreatic body and tail who was diagnosed with locally advanced SMARCB1-deficient undifferentiated pancreatic carcinoma with rhabdoid features, treated with radical resection and adjuvant chemotherapy, and has achieved 18-month disease-free survival ongoing at the time of article publication. We identify and contrast our case with 15 similar tumors reported in the English literature, briefly discuss the biology of this tumor, its relationship to malignant rhabdoid tumors of childhood, the role of SMARCB1 and its parent complex switch/sucrose-non-fermentable chromatin remodeling complex (SWI/SNF) in modulating the behavior of pancreatic malignancy, and the potential therapeutic avenues available for SWI/SNF-mutated malignancies.

Undifferentiated carcinoma of the pancreas with osteoclast-like giant cells: a case report

BACKGROUND

Undifferentiated carcinomas of the pancreas with osteoclast-like giant cells (UCPOGC) are rare pancreatic neoplasms that account for less than 1% of all pancreatic malignancies. This case report of a 54-year-old male with metastatic UCPOGC adds to the existing literature and further ascertains the clinical and imaging features, treatment options, and prognosis of this rare entity.

CASE PRESENTATION

We present the detailed clinical course of a 54-year-old Asian male patient with UCPOGC, with focus on the relevant clinical features and imaging findings that are characteristic of this disease entity.

CONCLUSIONS

UCPOGC is an extremely rare pancreatic tumor with a unique histopathology and clinical course. It is often difficult to distinguish UCPOGCs from other pancreatic tumors, such as traditional pancreatic ductal adenocarcinomas (PDAC), on imaging, and it therefore remains a pathological diagnosis. Surgery is generally regarded as the first-line treatment option, and the roles of chemotherapy and radiation are unclear. Due to the exceeding rarity of this tumor, large-scale clinical studies are not feasible. Therefore, it is important to share individual insights and experiences to improve our understanding and care for patients with this devastating disease.

Comprehensive review of undifferentiated carcinoma of the pancreas: from epidemiology to treatment

Undifferentiated carcinoma (UC) of the pancreas is a rare subtype of pancreatic cancer displaying no definitive direction of differentiation. UC has been reported as a highly aggressive malignant neoplasm, with a median overall survival of <1 year, except for several surgical series. On the other hand, UC tissue sometimes contains non-neoplastic osteoclast-like giant cells (OGCs), and such cases have been reported to have relatively longer survival. Thus, the World Health Organization (WHO) classification histologically distinguishes UC with OGCs (UCOGCs) from UC, and UCs were subclassified into three subtypes: anaplastic UC, sarcomatoid UC and carcinosarcoma. However, still less is known about UC due to its rarity, and such situations lead to further difficulties in treatment for UC. To date, only surgical resection can offer curative treatment for patients with UC, and no clear evidence for chemotherapy exists for them. However, a retrospective cohort study and case reports showed that relatively promising results paclitaxel-containing regimens for treatment of patients with unresectable UC. Furthermore, high programmed cell death protein 1 expression has been reported in sarcomatoid UCs and UCOGCs, and promising responses to anti-programmed death-ligand 1 therapy have been described in case reports of UCOGCs. Recent advances in chemotherapeutic agents and molecular technologies are opening up the possibilities for expanded treatments.

The Dual Role of Necroptosis in Pancreatic Ductal Adenocarcinoma

Pancreatic cancer (PC) is the seventh leading cause of cancer-related death. PC incidence has continued to increase by about 1% each year in both men and women. Although the 5-year relative survival rate of PC has increased from 3% to 12%, it is still the lowest among cancers. Hence, novel therapeutic strategies are urgently needed. Challenges in PC-targeted therapeutic strategies stem from the high PC heterogeneity and from the poorly understood interplay between cancer cells and the surrounding microenvironment. Signaling pathways that drive PC cell growth have been the subject of intense scrutiny and interest has been attracted by necroptosis, a distinct type of programmed cell death. In this review, we provide a historical background on necroptosis and a detailed analysis of the ongoing debate on the role of necroptosis in PC malignant progression.

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.

SMARCB1/INI1 loss in skull base conventional chordomas: a clinicopathological and molecular analysis

Introduction

The loss of SMARCB1/INI1 protein has been recently described in poorly differentiated chordoma, an aggressive and rare disease variant typically arising from the skull base.

Methods

Retrospective study aimed at 1) examining the differential immunohistochemical expression of SMARCB1/INI1 in conventional skull base chordomas, including the chondroid subtype; 2) evaluating SMARCB1 gene deletions/copy number gain; and 3) analyzing the association of SMARCB1/INI1 expression with clinicopathological parameters and patient survival.

Results

65 patients (35 men and 30 women) affected by conventional skull base chordoma, 15 with chondroid subtype, followed for >48 months after surgery were collected. Median age at surgery was 50 years old (range 9-79). Mean tumor size was 3.6 cm (range 2-9.5). At immunohistochemical evaluation, a partial loss of SMARCB1/INI1 (>10% of neoplastic examined cells) was observed in 21 (32.3%) cases; the remaining 43 showed a strong nuclear expression. Fluorescence in situ hybridization (FISH) analysis was performed in 15/21 (71.4%) cases of the chordomas with partial SMARCB1/INI1 loss of expression. Heterozygous deletion of SMARCB1 was identified in 9/15 (60%) cases and was associated to copy number gain in one case; no deletion was found in the other 6 (40%) cases, 3 of which presenting with a copy number gain. No correlations were found between partial loss of SMARCB1/INI1 and the clinicopathological parameters evaluated (i.e., age, tumor size, gender, tumor size and histotype). Overall 5-year survival and 5-year disease-free rates were 82% and 59%, respectively. According to log-rank test analysis the various clinico-pathological parameters and SMARCB1/INI1 expression did not impact on overall and disease free-survival.

Discussion

Partial loss of SMARCB1/INI1, secondary to heterozygous deletion and/or copy number gain of SMARCB1, is not peculiar of aggressive forms, but can be identified by immunohistochemistry in a significant portion of conventional skull base chordomas, including the chondroid subtype. The variable protein expression does not appear to correlate with clinicopathological parameters, nor survival outcomes, but still, it could have therapeutic implications.

SWI/SNF-deficient Malignancies: Optimal Candidates for Immune-oncological Therapy?

Inactivation of different subunits of the SWItch/sucrose nonfermentable (SWI/SNF) chromatin remodeling complex has emerged as one of the most frequent genetic pathways driving a variety of neoplasms of diverse histogenesis, originating in different organs. With few exceptions, most SWI/SNF-deficient malignancies pursue a highly aggressive clinical course resulting in widespread disease dissemination either at or soon after diagnosis, ultimately causing patients' death soon after diagnosis, despite the apparently curative treatment intention. To date, no satisfactorily effective systemic chemotherapy has been established for treating these diseases. This disappointing finding underlines the urgent need for an effective systemic therapy that would enable sufficient intermediate to long-term disease control. Recently, SWI/SNF-deficiency has increasingly emerged as pivotal in cancer immunogenicity and hence a promising biomarker predicting response to immune-checkpoint inhibition therapy utilizing several recently established drugs. This review summarizes the most recent literature on this topic with emphasis on the entities that most likely represent suitable candidates for immune therapy.

Cytologic, histologic, and molecular features of pancreatic sarcomatoid undifferentiated carcinoma with heterologous osteosarcomatous transformation

Fine-needle aspiration (FNA) is a minimally invasive and effective modality to diagnose pancreatic ductal adenocarcinoma. However, some histologic subtypes of ductal adenocarcinoma are rarely encountered and challenging to diagnose on FNA/small biopsies. To date, cytohistologic features of pancreatic sarcomatoid undifferentiated carcinoma with heterologous elements have not been thoroughly described. An 83-year-old man with lower back pain was found to have an incidental pancreatic neck mass. FNA biopsy of the mass showed rare markedly atypical, large, pleomorphic cells in a background of abundant calcifications/bone formation without areas of conventional adenocarcinoma. A diagnosis of "Malignant neoplasm with osteosarcomatous differentiation" was rendered on the FNA specimen. Subsequently, a Whipple resection revealed a 4.1 cm lobulated, calcified pancreatic mass. Microscopic examination showed a heavily calcified/ossified mass with adjacent areas of a highly cellular malignant spindle cell proliferation and admixed large, pleomorphic tumor cells; no background conventional adenocarcinoma was identified. Cytokeratin immunostains MNF116 and CK19 were positive in a large subset of the malignant spindle cells, and AE1.3/CAM5.2 showed patchy weak staining. Molecular testing revealed mutations in KRAS, TP53, BRCA2, NTRK3, EPHA2, MYD88, and CBL. No reportable fusions were detected. The final diagnosis was "Sarcomatoid undifferentiated carcinoma with heterologous elements (osteosarcomatous differentiation)." Definitive diagnosis of extremely rare subtypes of ductal adenocarcinoma is challenging on FNA biopsies. In this case, cytologic evaluation was helpful in making an early diagnosis of a malignant neoplasm with highly unusual features, prompting appropriate triage and early surgical resection of a sarcomatoid undifferentiated carcinoma with prominent osteosarcomatous differentiation.

Yolk sac tumor of postpubertal-type does not exhibit immunohistochemical loss of SMARCB1/INI1 and SMARCA4/BRG1…but choriocarcinoma?

The recently described SWI/SNF complex-deficient sinonasal carcinoma (SMARCB1 & SMARCA4) may exhibit a yolk sac-like morphology. Tumors with similar features (yolk sac-like histology combined with the immunohistochemical loss of SMARCB1/INI1 and/or SMARCA4/BRG1) have also been described in other sites, such as the female genital tract. In this study, we immunohistochemically assessed SMARCB1/INI1 and SMARCA4/BRG1 expression to evaluate if these proteins could be involved in the pathogenesis of testicular yolk sac tumors of postpubertal type (YSTpt). Specifically, we analyzed a retrospective case series comprising pure YSTpt and mixed germ cell tumors of the testis (GCTT) with YSTpt components. In the present study, no testicular YSTpt showed loss of SMARCB1/INI1 (0/24, 0%) or SMARCA4/BRG1 (0/24, 0%). However, testicular choriocarcinoma (CHC) and isolated syncytiotrophoblast cells (iSTCs) demonstrated abnormal staining patterns for SMARCA4/BRG1 [CHC: 4/4 (100%); iSTCs: 12/12 (100%), respectively], including focal or diffuse loss of expression in a subset of cases. The results of our study suggest that functional loss of SMARCA4/BRG1 represents a recurrent event that may be relevant for the pathogenesis of a subset of testicular CHC.

Undifferentiated Pancreatic Carcinomas, Clinical Features and Therapeutic Options: What We Know

Undifferentiated pancreatic carcinomas are rare malignant tumors of the pancreas that are very aggressive and challenging to diagnose. The WHO categorizes them into undifferentiated osteoclast-like giant cell, sarcomatoid, and rhabdoid pancreatic carcinomas. Patients present with nonspecific symptoms such as jaundice, vague abdominal or back pain and itchy skin. Their histological characteristics include positive pan-cytokeratin mononuclear pleomorphic cells, osteoclast-like giant cells and CD68. Patients may have KRAS, TP53 and SMAD4 alterations, homozygous deletions of CDKN2A and CDKN2B, as well as INI1 deficiency. Surgical resection is the only curative treatment. Patients may benefit from postoperative adjuvant therapy. There are no widely accepted guidelines specific to this type of tumor; however, some chemotherapy regimens may be promising. The patient prognosis is mostly poor, especially in patients with unresectable tumors. However, several studies have shown patients achieving long-term survival with adjuvant therapy. In conclusion, although undifferentiated pancreatic carcinoma is rare and very aggressive, there is still potential for improved patient survival with proper diagnosis and treatment.

Relationship between cellular morphology and abnormality of SWI/SNF complex subunits in pancreatic undifferentiated carcinoma

PURPOSE

Pancreatic undifferentiated carcinoma (UDC) is a rare tumor with a worse prognosis than pancreatic ductal adenocarcinoma (PDAC). Recent study showed that UDC exhibits loss of SMARCB1, which is one of the subunits of the SWI/SNF complex. However, whether there are abnormalities of other SWI/SNF complex subunits in UDC has remained unknown. In this study, we attempted to clarify whether the loss of SWI/SNF complex subunits is related to the pathogenesis of UDC by comparing undifferentiated component (UC) and ductal adenocarcinoma component (DAC).

METHODS

Genetic analysis of the ten UCs and six DACs was performed. The expression of ARID1A, SMARCA2, SMARCA4, SMARCB1, SMARCC1, and SMARCC2 in formalin-fixed, paraffin-embedded tumor tissues collected by surgical resection from 18 UDC patients was evaluated immunohistochemically. Moreover, two pancreatic cell lines were evaluated for the effects of siARID1A on the mRNA and protein expression of E-cadherin, vimentin, and epithelial-mesenchymal transition (EMT)-related markers by qRT-PCR, western blotting, and immunofluorescence staining.

RESULTS

UCs tended to have a higher frequency of mutation in ARID1A, SMARCA4, and SMARCC2 than DACs. Immunohistochemically, UCs revealed reduced/lost expression of ARID1A (72%), SMARCB1 (44%), SMARCC1 (31%), and SMARCC2 (67%). Reduced/lost expression of ARID1A, SMARCB1, and SMARCC2 was significantly more frequently observed in UCs than in DACs. In the pancreatic cell lines, western blotting and qRT-PCR showed that the downregulation of ARID1A increased the expression of vimentin and EMT-related markers.

CONCLUSION

Our results suggest that the abnormality of SWI/SNF complex subunits, especially ARID1A, is one of the factors behind the morphological change of UDC.

Genomic characterization of undifferentiated sarcomatoid carcinoma of the pancreas

Undifferentiated sarcomatoid carcinoma (USC) of the pancreas is a rare but especially aggressive variant of pancreatic ductal adenocarcinoma (PDAC), composed of at least 80% of sarcomatoid cells. This study aimed to elucidate its clinicopathological and molecular features. The study cohort included 10 patients with pancreatic USC. Clinicopathological parameters were determined for each patient. The molecular profile was investigated using next-generation sequencing (NGS). Histologically, all tumors were hypercellular neoplasms with spindle-shaped or sarcomatoid cells. All patients showed vascular and perineural invasion. Most patients had a poor prognosis. NGS showed important similarities with conventional PDAC, including frequent alterations in the classic PDAC drivers, KRAS (100% of cases), TP53 (90%), and CDKN2A (60%). There were also some important distinctions from conventional PDAC: 1) SMAD4, a typical PDAC driver gene, was mutated in only one case (10%); 2) Another distinctive molecular feature was the recurrent KRAS amplification (30% of cases), which is very rare in conventional PDAC. It has been previously reported in another subtype of pancreatic undifferentiated carcinoma, the rhabdoid variant, and may be a key event leading to the acquisition of an undifferentiated phenotype in a subgroup of cases; 3) Lastly, in two different cases, we detected two potentially actionable targets, not belonging to the typical PDAC molecular landscape, such as MCL1 amplification and POLQ mutation. Our study sheds light on this rare tumor type, which shows aggressive biological behavior and few druggable alterations. The most distinctive molecular features of pancreatic USC are the paucity of SMAD4 alterations and recurrent KRAS amplification.

SWI/SNF Complex-deficient Undifferentiated Carcinoma of the Gastrointestinal Tract: Clinicopathologic Study of 30 Cases With an Emphasis on Variable Morphology, Immune Features, and the Prognostic Significance of Different SMARCA4 and SMARCA2 Subunit Deficiencies

Undifferentiated carcinoma of the gastrointestinal tract has variable rhabdoid features. Expression of switch/sucrose nonfermenting (SWI/SNF) complex subunits is reportedly lost in a portion of cases; however, the prognostic significance of this loss remains unknown. Herein, 30 undifferentiated carcinoma cases were assessed for the expression of 4 SWI/SNF complex subunits (SMARCB1, SMARCA2, SMARCA4, and ARID1A). Tumor origin sites comprised stomach (40.0%), large intestine (20.0%), small intestine (16.7%), lower esophagus and stomach fundus (13.3%), ileocecal junction (3.3%), rectum (3.3%), and pancreas (3.3%). The tumors were composed of epithelioid neoplastic cells arranged in diffuse solid or discohesive sheets, nests, cords, poor cohesive pseudoglandular, and trabecular patterns. Rhabdoid tumor cells were identified in 66.7% (20/30) of cases. In total, 29/30 (96.7%) showed complete loss of at least 1 SWI/SNF subunit: SMARCA4-/SMARCA2- (11), isolated SMARCA4- (2), SMARCA4-/SMARCA2 unknown (6), isolated SMARCA2- (7), SMARCA2-/ARID1A- (1), and isolated ARID1A- (2). Negative or decreased expression (≤10% positive) of pan-cytokeratin was observed in 58.6% (17/29) of cases. In addition, 66.7% (20/30) of patients were late-stage (III or IV), and 65.2% (15/23) of stage IIB to IV patients succumbed to the disease at a mean clinical follow-up of 12.7 months. Specifically, patients with loss of SMARCA4 expression had the worst overall survival (P=0.028) and disease-free survival (P=0.006) rates, compared with those with SMARCA4 expression. The loss or decreased expression of epithelial markers is thus common in SWI/SNF complex-deficient undifferentiated carcinoma of the gastrointestinal tract, and loss of SMARCA4 correlates with poor prognosis.

Cytopathology of solid pancreatic neoplasms: An algorithmic approach to diagnosis

The classification and management of solid pancreatic neoplasms has expanded significantly in recent years because of advances in immunohistochemical markers, molecular diagnostics, and therapeutics. Solid pancreatic masses are subdivided into 1) ill-defined, scirrhous, and stroma-rich (ductal adenocarcinoma) and 2) well circumscribed, cellular, and stroma-poor (including neuroendocrine neoplasms, acinar cell carcinoma, pancreatoblastoma, and solid-pseudopapillary neoplasm). Definitive diagnosis, particularly of stroma-poor, circumscribed tumors, requires the incorporation of radiologic and cytologic findings, along with the judicious use of (broad, but limited) immunohistochemical panels (pancytokeratin and neuroendocrine [synaptophysin], acinar [trypsin], and solid-pseudopapillary neoplasm [β-catenin] markers), along with unstained slides. Depending on the initial results, immunohistochemical panels should be expanded to include more confirmatory (acinar and neuroendocrine) markers. This ensures that adequate material is available for definitive diagnosis/subclassification and, in some cases, grading, and/or molecular studies, particularly of grade 3 neuroendocrine neoplasms and mixed-lineage tumors. The objective of this review is to expand the understanding of the cytomorphology of solid pancreatic neoplasms using an integrated, multidisciplinary approach in their diagnosis. Knowledge and understanding of recent updates in the classification of solid pancreatic neoplasms ensures that cytopathologists appropriately triage specimens, judiciously use and interpret ancillary studies, and incorporate these results in reporting.

A case of retroperitoneal tumor displaying epithelial differentiation, prominent myxoid stroma and loss of INI1/SMARCB1

The clinicopathological spectrum of INI1 deficient tumors is expanding. Epithelioid sarcoma (ES) is a rare sarcoma of uncertain differentiation, more often occurring in the extremities and uncommonly in the deep soft tissues. Histopathologically, it manifests in the form of classical, proximal, or hybrid types, the latter two characterized by rhabdoid cytomorphology. Immunohistochemically, ESs display loss of INI1/SMARCB1 and genetically associated with high percentage of SMARCB1 deletions

We report an extremely uncommon case of a retroperitoneal tumor in a 42-year-old male, who presented with abdominal discomfort. Radiologic imaging disclosed a 12 cm-sized retroperitoneal mass without involvement of any organ parenchyma. The patient underwent tumor excision with left-sided nephrectomy at another hospital. A review of the paraffin-embedded tissue sections revealed a multinodular tumor, composed of dyscohesive epithelioid tumor cells and focally arranged in cords, containing moderate to abundant, eosinophilic cytoplasm, vesicular nuclei, containing prominent nucleoli, including cells with rhabdoid cytomorphology, in a conspicuous myxoid stroma. A focal tumor area resembled proximal-type of ES. Immunohistochemically, tumor cells displayed positivity for pan cytokeratin (AE1/AE3), epithelial membrane antigen (EMA), vimentin and focally for CA125, while these were negative for CD34, S100 protein, CKIT, DOG1, and INI1/SMARCB1.

To the best of our knowledge, this constitutes the first case of a malignant tumor with epithelioid morphology, displaying myxoid matrix and loss of INI1/SMARCB1, resembling a myxoid variant of an epithelioid sarcoma and myoepithelioma-like tumor of the vulvar tumor, occurring in the retroperitoneum. A review of similar cases, differential diagnosis and treatment-associated implications are presented.

Pathology and Molecular Characteristics of Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer. However, it should be kept in mind that there are other pancreatic cancers that are classified by their cellular lineage: acinar cell carcinomas (acinar differentiation), neuroendocrine neoplasms (arising from the islets), solid-pseudopapillary neoplasms (showing no discernible cell lineage), and pancreatoblastomas (characterized by multiphenotypic differentiation, including acinar endocrine and ductal). This article focuses on the molecular and pathology alterations in PDAC.

Pleomorphic (giant cell) carcinoma revisited: A historical perspective and conceptual reappraisal

The term pleomorphic "giant cell" carcinoma was coined by Sommers and Meissner in 1954 for a pancreatic carcinoma variant showing a "sarcoma-like transformation" and characterized by an admixture of undifferentiated cells with striking variation in size and shape. Based on the predominant cell type, four patterns were recognized: spindle cell (sarcomatoid), pleomorphic "giant cell", osteoclastic giant cell-rich, and anaplastic round cell. These four basic patterns frequently coexisted within same tumor, albeit to a significantly variable extent. Follow-up series further characterized the entity, expanded its topographic distribution to include almost all organ systems, and illustrated its morphological and phenotypic homology among different organs. Although resemblance of the neoplastic cells to rhabdomyoblasts was already pointed out by Stout in 1958, the term "rhabdoid" (introduced in 1978 for specific kidney tumors) was not used for carcinomas until 1993. Review of the old and recent literature indicates pleomorphic "giant cell" carcinoma is not an entity but a morphological pattern in the spectrum of undifferentiated (anaplastic) and sarcomatoid carcinoma that can originate in any organ, either in a pure form or as a dedifferentiated carcinoma component. These tumors fall into two major categories: a monomorphic (variable admixture of small or larger "gemistocyte-like" rhabdoid cells and epithelioid cells) and a pleomorphic (bizarre large polygonal, spindled, or multinucleated malignant cells) subtype. The few available genetic studies suggest close association of the monomorphic type with SWI/SNF pathway defects, while bizarre-looking pleomorphic tumors usually harbor complex and heterogeneous genetic alterations. Most tumors dominated by the pleomorphic "giant cell" pattern are extremely aggressive, resulting in death, soon after diagnosis, irrespective of treatment modalities. This review gives an historical account on the evolution of the pleomorphic "giant cell" carcinoma concept with special reference to their relationship to SWI/SNF complex alterations.

Undifferentiated and dedifferentiated urological carcinomas: lessons learned from the recent developments

Loss of the morphological and immunophenotypic characteristics of a neoplasm is a well-known phenomenon in surgical pathology and occurs across different tumor types in almost all organs. This process may be either partial, characterized by transition from well differentiated to undifferentiated tumor component (=dedifferentiated carcinomas) or complete (=undifferentiated carcinomas). Diagnosis of undifferentiated carcinoma is significantly influenced by the extent of sampling. Although the concept of undifferentiated and dedifferentiated carcinoma has been well established for other organs (e.g. endometrium), it still has not been fully defined for urological carcinomas. Accordingly, undifferentiated/ dedifferentiated genitourinary carcinomas are typically lumped into the spectrum of poorly differentiated, sarcomatoid, or unclassified (NOS) carcinomas. In the kidney, dedifferentiation occurs across all subtypes of renal cell carcinoma (RCC), but certain genetically defined RCC types (SDH-, FH- and PBRM1- deficient RCC) seem to have inherent tendency to dedifferentiate. Histologically, the undifferentiated component displays variable combination of four patterns: spindle cells, pleomorphic giant cells, rhabdoid cells, and undifferentiated monomorphic cells with/without prominent osteoclastic giant cells. Any of these may occasionally be associated with heterologous mesenchymal component/s. Their immunophenotype is often simple with expression of vimentin and variably pankeratin or EMA. Precise subtyping of undifferentiated (urothelial versus RCC and the exact underlying RCC subtype) is best done by thorough sampling supplemented as necessary by immunohistochemistry (e.g. FH, SDHB, ALK) and/ or molecular studies. This review discusses the morphological and molecular genetic spectrum and the recent develoments on the topic of dedifferentiated and undifferentiated genitourinary carcinomas.

[Ductal adenocarcinoma of the pancreas: subtypes and molecular pathology]

Ductal adenocarcinoma is the most common tumor of the pancreas. Although relatively rare, it poses one of the greatest oncological challenges because of its poor prognosis, which has so far only slightly improved. Progress has been made in the more precise classification and standardization of the morphological assessment. In the current WHO classification, prognostically relevant subtypes are clearly delimited among themselves and from ductal adenocarcinoma not otherwise specified (NOS). In the recent TNM classification, a size-based T‑category was introduced. Diagnostically, the histological assessment of the resection specimen is relatively easy; on the other hand, assessment of the fine-needle biopsy from the primary tumor or a liver metastasis is still difficult. The molecular stratification of ductal adenocarcinoma and the other pancreatic neoplasms has made great progress. This not only defined the genetics of tumor entities, but also identified the prognosis and biology of tumor groups on the basis of RNA expression patterns. The range of treatment could be expanded by targeted molecular therapies (especially for patients with BRCA1/2 germline mutations, NTRK- or NRG1-fusions, or oncogenic BRAF and PIK3CA mutations as well as tumors with microsatellite instability (MSI)), even if targeted therapies are currently only available for a minority of patients (<10%).

Mesenchymal/non-epithelial mimickers of neuroendocrine neoplasms with a focus on fusion gene-associated and SWI/SNF-deficient tumors

Mimickers of neuroendocrine neoplasms (NEN) include a number of important pitfall tumors. Here, we describe our experience with mesenchymal mimics of NENs to illustrate their spectrum and draw the attention particularly to a group of mesenchymal/non-epithelial neoplasms (MN) that combine epithelioid histology with neuroendocrine (NE-) features and peculiar genetic abnormalities. In a consultation series of 4498 cases collected between 2009 and 2021, 2099 neoplasms expressing synaptophysin and/or chromograninA were reviewed and analyzed. A total of 364 (18%) were diagnosed as non-NENs, while the remaining tumors were NEN. The group of mesenchymal/non-epithelial neoplasms with NE-features (MN-NE) included 31/364 (8%) cases. These mostly malignant neoplasms showed an epithelioid morphology. While all but one tumor expressed synaptophysin, mostly patchy, only 10/29 (34%) co-expressed chromograninA. A total of 13/31 (42%) of the MN-NE showed EWSR1-related gene fusions (6 Ewing sarcomas, 5 clear cell sarcomas, and 1 desmoplastic small round cell tumor, 1 neoplasm with FUS-CREM gene fusion) and 7 (23%) were SWI/SNF (SMARCB1 or SMARCA4)-deficient neoplasms. The remaining MN-NE included synovial sarcoma, sclerosing epithelioid mesenchymal neoplasm, melanoma, alveolar soft part sarcoma, solitary fibrous tumor, and chordoma. A total of 27/31 MN-NE were from the last 8 years, and 6 of them were located in the pancreas. Eleven MN-NE were initially diagnosed as neuroendocrine carcinomas (NECs). MN-NE with epithelioid features play an increasing role as mimickers of NECs. They mostly belong to tumors with gene fusions involving the EWSR1 gene, or with SWI/SNF complex deficiency. Synaptophysin expression is mostly patchy and chromograninA expression is infrequent in MN-NE of this series and data extracted from literature.

Cytomorphologic Spectrum of SMARCB1-Deficient Soft Tissue Neoplasms

OBJECTIVES

The SWI/SNF complex core subunit SMARCB1 is inactivated in a variety of neoplasms that share characteristic "rhabdoid" cytomorphology. The aim of this study was to evaluate SMARCB1-deficient soft tissue neoplasms on cytology to identify diagnostic clues.

METHODS

Eleven SMARCB1-deficient tumors, including six epithelioid sarcomas, three malignant rhabdoid tumors, one epithelioid malignant peripheral nerve sheath tumor (MPNST), and one poorly differentiated chordoma with fine-needle aspiration (FNA), serous effusion, or touch prep (TP) from two institutions, were included. Targeted next-generation sequencing (NGS) was performed in two cases.

RESULTS

Evaluation of FNA (n = 4), effusion (n = 4), and TP (n = 3) in nine adult and two pediatric patients demonstrated cellular samples (n = 11), epithelioid cells with rhabdoid morphology (n = 9), eccentrically located nuclei with prominent nucleoli (n = 7), and cytoplasmic bodies (n = 4); two patients were diagnosed on FNA with cell block. Immunohistochemistry (IHC) demonstrated SMARCB1 loss in all cases and keratin and/or EMA expression in all but the epithelioid MPNST; NGS identified SMARCB1 inactivation in both cases.

CONCLUSIONS

SMARCB1-deficient soft tissue neoplasms comprise a variety of tumors with epithelioid morphology and frequent expression of keratin and/or EMA. Recognition of characteristic rhabdoid morphology on cytology can prompt IHC and/or NGS testing for SMARCB1 deficiency and help establish the diagnosis.

INI1-Deficient Thyroid Carcinoma is an Aggressive Disease with Epithelioid and Rhabdoid Phenotype. A Case Report, Survey of INI1 Expression in Thyroid Lesions and Literature Review

Integrase interactor 1 (INI1)-deficient carcinomas, recently described in several sites including the head and neck, are associated with basaloid or rhabdoid histology and aggressive behavior irrespective of origin. INI1-deficient thyroid carcinoma is extremely rare. We present here the phenotype and genotype of an INI1-deficient thyroid carcinoma and report on the INI1 protein expression in various thyroid lesions. Case report with clinicopathologic and molecular characterization and INI1 assessment in 184 thyroid lesions. A 67-year-old woman presented with globus sensation due to a large thyroid mass with extrathyroid extension, focal necrosis and cervical and mediastinal nodal involvement. Histologically, tumor cells had a solid, alveolar and pseudopapillary architecture in a myxoid stroma, exhibited monomorphic epithelioid and focal rhabdoid/plasmacytoid morphology and lacked glandular, squamous or follicular cell differentiation. Tumor cells were positive for AE1/AE3 and CK18 but negative for TTF1, thyroglobulin and PAX8. INI1 nuclear expression was absent. A frameshift SMARCB1/INI1 mutation was detected. In addition, TET2 and Notch1 mutations were present but alterations of BRAF, RET, PAX8/PPAR8 or RAS were not identified. Patient death occurred 14 months after diagnosis from post-therapeutic complications. None of the 184 benign and malignant thyroid lesions tested, including 12 poorly and undifferentiated thyroid carcinomas, were INI1-deficient. INI1-deficient thyroid carcinoma shares the phenotype, genotype and biology of other INI1-deficient tumors. Epithelioid and plasmacytoid/rhabdoid changes are most frequent whereas basaloid morphology is not reported, in contrast with sinonasal tumors. Poorly differentiated and undifferentiated thyroid tumors with epithelioid or rhabdoid morphology should be tested for INI1 protein expression to better characterize these aggressive neoplasms and identify patients eligible for targeted therapy.

Extended pancreato-duodenectomy coupled with adjuvant chemotherapy for SMARCB1/INI1 deficient pancreatic carcinoma: A case report and literature review

Introduction

SMARCB1/INI1 gene deletion appears to be associated with a rare, malignant and aggressive form of pancreatic carcinoma whose diagnosis is challenging. Our objective is to illustrate that the tumor may masquerade as a duodenal papillary carcinoma, be difficulty to identify on diagnostic imaging and that making an accurate diagnosis may be challenging, however surgical resection may be possible.

Case report

We present a case of a 24-year old male patient presenting with jaundice and itchy skin, elevated TBIL, AST, ALP and CA125. A 2.2 × 1.7 cm pancreatic nodule, later diagnosed as a SMARCB1/INI deficient pancreatic carcinoma was detected on Endoscopic Ultrasound - Fine Needle Aspiration (EUS-FNA). The patient was successfully treated with extended pancreato-duodenectomy coupled with adjuvant chemotherapy, a 7 × 5 × 5 cm tumor resected.

Discussion

SMARCB1/INI deficient pancreatic carcinoma has been reported in couple of other articles. However, unlike other cases, in our case identification and accurate assessment of the tumor was particularly difficulty both on imaging and during operation. Our patient has thus far had a positive outcome with no recurrence.

Conclusion

For rare forms of pancreatic carcinoma, identification and assessment of the tumor size may be challenging on imaging and during operation. However, careful assessment should be performed before ruling out surgical resection. Furthermore, adjuvant chemotherapy may be beneficial to the patient.

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SMARCB1/INI gene deletion is associated with undifferentiated carcinoma characterized by malignancy and aggressiveness.

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This case highlights the ambiguity in manifestation and diagnosis of SMARCB1 pancreatic carcinoma.

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Assessment and accurate determination of the tumor size may not be possible on imaging and preoperatively.

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Adjuvant chemotherapy may be beneficial to patient prognosis post-surgery.

SMARCB1/INI1-deficient tumors of adulthood

The SMARCB1/INI1 gene was first discovered in the mid-1990s, and since then it has been revealed that loss of function mutations in this gene result in aggressive rhabdoid tumors. Recently, the term "rhabdoid tumor" has become synonymous with decreased SMARCB1/INI1 expression. When genetic aberrations in the SMARCB1/INI1 gene occur, the result can cause complete loss of expression, decreased expression, and mosaic expression. Although SMARCB1/INI1-deficient tumors are predominantly sarcomas, this is a diverse group of tumors with mixed phenotypes, which can often make the diagnosis challenging. Prognosis for these aggressive tumors is often poor. Moreover, refractory and relapsing progressive disease is common. As a result, accurate and timely diagnosis is imperative. Despite the SMARCB1/INI1 gene itself and its implications in tumorigenesis being discovered over two decades ago, there is a paucity of rhabdoid tumor cases reported in the literature that detail SMARCB1/INI1 expression. Much work remains if we hope to provide additional therapeutic strategies for patients with aggressive SMARCB1/INI1-deficient tumors.

Pancreatic INI1-deficient undifferentiated rhabdoid carcinoma achieves complete clinical response on gemcitabine and nab-paclitaxel following immediate progression on FOLFIRINOX: a case report

INTRODUCTION

INI1-deficient undifferentiated rhabdoid carcinoma is a rare pancreatic carcinoma for which the optimal treatment is unknown. Pancreatic ductal adenocarcinoma, the most common histology of pancreas cancer, is treated with combination chemotherapy in the advanced setting, a strategy supported by strong evidence in well powered studies. In patients with excellent performance status, first-line treatment usually consists of the three-drug regimen FOLFIRINOX, with the combination of gemcitabine with nab-paclitaxel, typically less toxic than the three-drug regimen, reserved for second-line therapy. Given the lack of published reports describing treatment outcomes for patients with rare forms of pancreatic cancer, the same treatment approach used for pancreatic ductal adenocarcinoma is typically employed.

OBSERVATION

This case describes a patient with metastatic pancreatic INI1-deficient undifferentiated rhabdoid carcinoma who was primarily resistant to FOLFIRINOX therapy but who then achieved an immediate, marked and sustained response to gemcitabine with nab-paclitaxel.

CONCLUSION

Given the lack of data informing on optimal management of INI1-deficient pancreatic undifferentiated rhabdoid carcinoma, and the exceptional response achieved by gemcitabine with nab-paclitaxel, this case report highlights a surprising and potentially informative anecdote. Additional studies are needed to confirm responses observed in this report which when taken together may strongly influence first-line therapy choice for this rare malignancy. Given the difficult in acquiring sufficient numbers of these rare histologies in any one institution, multi-institution collaboration in studying outcomes of rare pancreatic malignancies is likely essential.

A mucinous cystic neoplasm of the pancreas containing an undifferentiated carcinoma component and harboring the NRAS driver mutation

A woman in her 20s visited our hospital with a chief complaint of abdominal distension and back pain. She was diagnosed with a cystic tumor (diameter 16 cm) in the tail of the pancreas and underwent a combined distal pancreatectomy, splenectomy, and left adrenalectomy. Histopathologically, the tumor presented as a mucinous cystic neoplasm with an undifferentiated carcinoma component of the pancreas. In addition, the cells demonstrated a partial rhabdoid-like morphology. These findings were considered relatively typical for a mucinous cystic neoplasm in the tail of the pancreas in a young woman. However, NRAS mutation, which is rare in pancreatic tumors, was detected.

The role of the SWI/SNF chromatin remodeling complex in pancreatic ductal adenocarcinoma

ATP-dependent chromatin remodeling complexes are a group of epigenetic regulators that can alter the assembly of nucleosomes and regulate the accessibility of transcription factors to DNA in order to modulate gene expression. One of these complexes, the SWI/SNF chromatin remodeling complex is mutated in more than 20% of human cancers. We have investigated the roles of the SWI/SNF complex in pancreatic ductal adenocarcinoma (PDA), which is the most lethal type of cancer. Here, we reviewed the recent literature regarding the role of the SWI/SNF complex in pancreatic tumorigenesis and current knowledge about therapeutic strategies targeting the SWI/SNF complex in PDA. The subunits of the SWI/SNF complex are mutated in 14% of human PDA. Recent studies have shown that they have context-dependent oncogenic or tumor-suppressive roles in pancreatic carcinogenesis. To target its tumor-suppressive properties, synthetic lethal strategies have recently been developed. In addition, their oncogenic properties could be novel therapeutic targets. The SWI/SNF subunits are potential therapeutic targets for PDA, and further understanding of the precise role of the SWI/SNF complex subunits in PDA is required for further development of novel strategies targeting SWI/SNF subunits against PDA.

Epithelioid Sarcoma of the External Auditory Canal: An Uncommon Tumor at an Unusual Site and a Brief Overview of the Literature

We present a case (41 years old pregnant female) with epithelioid sarcoma arising in the left external auditory canal. On immunohistochemistry, the tumor cell diffusely expressed cytokeratins and showed patchy expression of ERG and CD34. The neoplastic cells demonstrated uniform loss of INI1-expression. Epithelioid sarcoma arising in the external auditory canal is rare. Awareness that ES may rarely arise at unusual sites is of critical importance in order to apply a broad enough panel in the immunohistochemical study, so a misdiagnosis of carcinoma can be avoided.

SWI/SNF-deficient cancers of the Gastroenteropancreatic tract: an in-depth review of the literature and pathology

The SWItch Sucrose non-fermentable (SWI/SNF) complex is a large, multi-subunit ATP-dependent nucleosome remodeling complex that acts as a tumor suppressor by modulating transcription. Mutations of SWI/SNF subunits have been described in relation to developmental disorders, hereditary SWI/SNF deficiency syndromes, as well as malignancies. In this review we summarize the current literature in regards to SWI/SNF-deficient tumors of the luminal gastrointestinal tract (GIT) and pancreas. As a group they range from moderately to undifferentiated tumors composed of monotonous anaplastic cells, prominent macronucleoli and a variable rhabdoid cell component. Deficiency of a SWI/SNF subunit is typified by complete loss of nuclear staining by immunohistochemistry for respective subunit.

Morphologic and Molecular Landscape of Pancreatic Cancer Variants as the Basis of New Therapeutic Strategies for Precision Oncology

To date, pancreatic cancer is still one of the most lethal cancers in the world, mainly due to the lack of early diagnosis and personalized treatment strategies. In this context, the possibility and the opportunity of identifying genetic and molecular biomarkers are crucial to improve the feasibility of precision medicine. In 2019, the World Health Organization classified pancreatic ductal adenocarcinoma cancer (the most common pancreatic tumor type) into eight variants, according to specific histomorphological features. They are: colloid carcinoma, medullary carcinoma, adenosquamous carcinoma, undifferentiated carcinoma, including also rhabdoid carcinoma, undifferentiated carcinoma with osteoclast-like giant cells, hepatoid carcinoma, and signet-ring/poorly cohesive cells carcinoma. Interestingly, despite the very low incidence of these variants, innovative high throughput genomic/transcriptomic techniques allowed the investigation of both somatic and germline mutations in each specific variant, paving the way for their possible classification according also to specific alterations, along with the canonical mutations of pancreatic cancer (KRAS, TP53, CDKN2A, SMAD4). In this review, we aim to report the current evidence about genetic/molecular profiles of pancreatic cancer variants, highlighting their role in therapeutic and clinical impact.

Loss of SMARCB1 expression in colon carcinoma

SMARCB1 is a tumor suppressor gene, which is part of SWI/SNF complex involved in transcriptional regulation. Recently, loss of SMARCB1 expression has been reported in gastrointestinal carcinomas. Our purpose was to evaluate the incidence and prognostic value of SMARCB1 loss in colon carcinoma (CC). Patients with stage III CC (n= 1695), and a second cohort of 23 patients with poorly differentiated CC were analyzed. Immunohistochemistry for SMARCB1 was performed on tissue microarrays, and cases with loss of expression were controlled on whole sections. Loss of SMARCB1 was compared with the clinico-pathological and molecular characteristics, and the prognostic value was evaluated. Loss of SMARCB1 was identified in 12 of 1695 (0.7%) patients with stage III CC. Whole section controls showed a complete loss in only one of these cases, corresponding to a medullary carcinoma. SMARCB1 loss was not associated with histological grade, tumor size nor survival. In the cohort of poorly differentiated CC, we detected 2/23 (8.7%) cases with loss of SMARCB1; one was rhabdoid while the other had medullary and mucinous histology. These 2 cases were deficient for MisMatched Repair (dMMR) and mutated for BRAF. SMARCB1 loss is rare in stage III CC, but appears more frequent in poorly differentiated CC.

SMARCB1/INI1-deficient pancreatic undifferentiated rhabdoid carcinoma mimicking solid pseudopapillary neoplasm: A case report and review of the literature

BACKGROUND

SMARCB1/INI1-deficient pancreatic undifferentiated rhabdoid carcinoma is a very aggressive tumor that is rarely reported in the literature. The tumor has a predominant rhabdoid cell component and different patterns of growth have been reported.

CASE SUMMARY

A 59-year-old woman presented with diffuse abdominal pain, increasing in severity and accompanied by weight loss, nausea, and vomiting. Imaging showed a pancreatic head mass. Fine needle aspiration demonstrated atypical epithelioid cells with a pseudopapillary growth pattern suggestive of solid pseudopapillary neoplasm. The excised neoplasm showed monotonous epithelioid and focally spindle cells with pseudopapillary structures, rhabdoid features, and loss of SMARCB1 protein expression with wild-type KRAS, consistent with a SMARCB1/INI1-deficient undifferentiated rhabdoid carcinoma. The patient’s condition deteriorated rapidly following surgery and she expired 3 mo post operation.

CONCLUSION

In this article, we report the first case of SMARCB1/INI1-deficient undifferentiated pancreatic rhabdoid carcinoma mimicking solid pseudopapillary neoplasm.

Malignant epithelial/exocrine tumors of the pancreas

Pancreatic malignant exocrine tumors represent the most important cause of cancer-related death for pancreatic neoplasms. The most common tumor type in this category is represented by pancreatic ductal adenocarcinoma (PDAC), an ill defined, stroma-rich, scirrhous neoplasm with glandular differentiation. Here we present the relevant characteristics of the most important PDAC variants, namely adenosquamous carcinoma, colloid carcinoma, undifferentiated carcinoma, undifferentiated carcinoma with osteoclast-like giant cells, signet ring carcinoma, medullary carcinoma and hepatoid carcinoma. The other categories of malignant exocrine tumors, characterized by fleshy, stroma-poor, circumscribed neoplasms, include acinar cell carcinoma (pure and mixed), pancreatoblastoma, and solid pseudopapillary neoplasms. The most important macroscopic, histologic, immunohistochemical and molecular hallmarks of all these tumors, highlighting their key diagnostic/pathological features are presented. Lastly, standardized indications regarding gross sampling and how to compile a formal pathology report for pancreatic malignant exocrine tumors will be provided.

SMARCB1-deficient carcinomas of the head and neck region: a cytopathologic characterization

INTRODUCTION

SMARCB1 encodes for a component of the SWI/SNF complex and is widely implicated in carcinogenesis. In the head and neck, SMARCB1-deficient carcinomas typically arise in the sinonasal tract but can be found at other sites. EZH2 inhibitors have emerged as potential targeted therapy against SWI/SNF-deficient tumors. We sought to characterize the cytomorphology of head and neck carcinomas with SMARCB1 deficiencies to identify potential candidates for targeted therapy.

MATERIALS AND METHODS

Head and neck carcinomas with SMARCB1 mutations were retrospectively identified and confirmed to be SMARCB1-deficient by both molecular (fluorescent in-situ hybridization or next generation sequencing) and immunohistochemical means. Cases with positive cytology were reviewed and their cytologic features cataloged.

RESULTS

A total of 19 specimens from 13 patients were reviewed, including 8 specimens from 7 sinonasal carcinomas, 4 specimens from 3 thyroid carcinomas, 3 specimens from 2 skin carcinomas, and 4 specimens from 1 carcinoma of unknown primary origin. High-grade features were common, including mitoses (11 of 19) necrosis (13 of 19) and multinucleation (16 of 19). Tumors showed either dense cytoplasm with distinct cell borders (10 of 19) or delicate cytoplasm with indistinct cell borders (9 of 19). Most tumors showed no distinct epithelial differentiation (12 of 19), while some (7 of 19) showed glandular or signet ring features. A minor cohort demonstrated rhabdoid cells (4 of 19).

CONCLUSIONS

Head and neck carcinomas with SMARCB1 deficiencies have a wide array of morphologies and tend to demonstrate high-grade features. Only a minor cohort demonstrate rhabdoid-type cells. Evaluation of SMARCB1 deficiency for potential targeted therapy should not be limited to tumors with rhabdoid morphology.

Loss of switch/sucrose non-fermenting complex protein expression in undifferentiated gastrointestinal and pancreatic carcinomas

AIMS

Undifferentiated carcinoma refers to an epithelial malignancy that lacks morphological evidence of differentiation. Recent studies have implicated the loss of constitutively expressed switch/sucrose non-fermenting (SWI/SNF) complex subunits in undifferentiated carcinomas of the gastrointestinal tract and other sites. In this study we examine the expression of SWI/SNF and mismatch repair (MMR) proteins in a series of undifferentiated carcinomas from the gastrointestinal tract and the pancreas.

METHODS AND RESULTS

We searched pathology databases from four Canadian health centres for primary undifferentiated carcinoma from gastrointestinal and pancreatic resection specimens. Upon review of 31 cases, 19 were confirmed to be undifferentiated carcinomas (eight colonic, six gastric, three pancreatic, one appendiceal and one duodenal). Immunohistochemical analysis of SMARCA4, SMARCA2, SMARCB1, ARID1A, ARID1B, MSH2, MSH6, MLH1 and PMS2 was performed on whole sections. Five of 19 (26%) showed loss of core SWI/SNF proteins (two loss of SMARCA4, one loss of SMARCB1 and two concurrent loss of ARID1A and ARID1B). SMARCA4, SMARCB1, or ARID1A/ARID1B-deficient undifferentiated carcinoma consistently exhibited sheet-like growth pattern, with cellular discohesion and rhabdoid morphology. Nine of 17 undifferentiated carcinomas tested were MMR-deficient by immunohistochemistry. In comparison, none of the 12 poorly differentiated carcinomas that were originally diagnosed as undifferentiated carcinomas showed loss of SMARCA4, SMARCA2, SMARCB1 or ARID1B.

CONCLUSIONS

Undifferentiated gastrointestinal/pancreatic carcinomas show frequent loss of expression of SWI/SNF complex proteins. The loss of these core components of SWI/SNF complex may contribute to the arrest of cellular differentiation, resulting in the undifferentiated histology and aggressive clinical behaviour.